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Disable ASLR on iOS applications

23 May

ASLR – Address Space Layout Randomization is an important exploit mitigation technique introduced in iOS 4.3. ASLR makes the remote exploitation of memory corruption vulnerabilities significantly more difficult by randomizing the application objects location in the memory. By default iOS applications uses limited ASLR and only randomizes part of the objects in the memory. The image compares the different memory sections for partial and full ASLR applications.

partial vs full ASLR - iOS

In order to take full advantage of the ASLR, the application has to compile with -fPIE -pie flag (“Generate Position-Dependent Code” build option in Xcode). This flag is automatically checked by default in the latest version of the XCode (from iOS 6). So, all the applications that are compiled in the latest SDK will automatically use full ASLR. To find out whether the application is compiled with PIE flag or not, connect the iPhone over SSH and execute the below command.

Otool –Vh ApplicaitonBinary

PIE enabled iOS app

The above image shows PIE at the end of the file header. It indicates that the Facebook application is compiled with PIE flag and uses the full ASLR.

During the pentest, ASLR might cause issues while reversing or decrypting the application. To overcome this problem, Peter Fillmore wrote an awesome tool removePIE that can be used to disable the ASLR of an iOS application. It disables the ASLR by flipping the PIE flag.

Steps to disable the ASLR of an iOS Application:

1. Download removePIE.zip and extract it.
2. Copy removePIE to the iPhone using the below SCP command (password is alpine).

SCP removePIE root@iPhoneIP:/var/root

3. The SCP command copies the removePIE file into /var/root directory on the iPhone. This can be verified by connecting to the iPhone over SSH.

copy removePIE to iPhone

4. Copy removePIE to the corresponding application’s home directory.

removePIE to application directory

5. To disable ASLR of an application, run the removePIE command on the application binary.

./removePIE ApplicationBinary

disable ASLR of iOS app

The above command takes a backup of the application binary, then flips the PIE flag and disables the ASLR. This can be confirmed by running the otool -Vh ApplicationBinary command.

PIE disabled

The above image does not show PIE flag in the file header. It confirms that the Facebook application no more uses the full ASLR.

Note: removePIE does not accept the application path as an argument. Supplying the binary path to the program, ends up with segment fault:11 exception. 

References:
1. http://www.peterfillmore.com/2013/01/removepie-tool-for-disabling-aslr-on.html
2. iOS 4 security evaluation white paper by Dai Zovi

 
 

Penetration testing of iPhone Applications – Part 4

15 Apr

In the first part of the article, we have discussed about the iPhone application traffic analysis. Second part of the article covered the privacy issues and property list data storage. Third part covered in-depth analysis of the iOS keychain data storage. In this part we will take a look at different types of files stored/created in the application’s home directory and other insecure data storage locations.

Sqlite storage

Sqlite is a cross-platform C library that implements a self-contained, embeddable, zero-configuration SQL database engine. Sqlite database does not need a separate server process and the complete database with multiple tables, triggers, and views is contained in a single disk file. The Sqlite database offers all the standard SQL constructs, including Select, Insert, Update and Delete. As Sqlite is portable, reliable and  small, it is an excellent solution for persistent data storage on iOS devices.

Sqlite library that comes with iOS is a lightweight and powerful relational database engine that can be easily embedded into an application. The library provides fast access to the database records. As the complete database is operated as a single flat file, applications can create local database files and manage the tables & records very easily. In general, iOS applications use the Sqlite database to store large and complex data as it offers good memory usage and speed. Sqlite database that comes with iOS does not have a builtin support for encryption. So most of the iOS applications store lots of sensitive data in plain text format in Sqlite files. For example, to provide offline email access, Gmail iOS application stores all the emails in a Sqlite database file in plain text format.

Unencrypted sensitive information stored in a Sqlite file can be stolen easily upon gaining physical access to the device or from the device backup. Also, if an entry is deleted, Sqlite tags the record as deleted but not purge them. So in case if an application temporarily stores and removes the sensitive data from a Sqlite file, deleted data can be recovered easily by reading the Sqlite Write Ahead Log.

The Sqlite files can be created with or without any file extention. Most common extentions are .sqlitedb &.db. The below article explains, how to view Sqlite files and how to recover the deleted data from Sqlite files on the iPhone. For this exercise, I have created a demo application called CardInfoDemo. CardInfoDemo is a self signed application, so it can only be installed on a Jailbroken iPhone. The CardInfo demo application accepts any username & password, then collects the credit card details from the user and stores it in a Sqlite database. Database entries are deleted upon logout from the app.

Steps to install the CardInfo application:

1. Jailbreak the iPhone.
2. Download the CardInfoDemo,ipa file -  Download link.
3. 
On Windows, download the iPhone configuration utility – Download link.
4. 
Open the iPhone configuration utility and drag the CardInfoDemo.ipa file on to it.

iPhone configuration utility

5. Connect the iPhone to the windows machine using USB cable. Notice that the connected device is listed in the iPhone configuration utility. Select the device and navigate to Applications tab. It lists the already installed applications on the iPhone along with our CardInfo demo app. Cardinfo demo iOS app install

6. Click on Install button corresponding to the CardInfo application and it installs the CardInfo application on to the iPhone.

cardinfo ios demo app

Steps to view  CardInfo Sqlite files:

1. On the Jailbroken iPhone, install OpenSSH and Sqlite3 from Cydia.
2. 
On windows workstation, download Putty.
3. 
Connect the iPhone and the workstation to the same Wi-Fi network. Note: Wi-Fi is required to connect the iPhone over SSH. If the Wi-Fi connection is not available SSH into the iPhone over USB.
4Run Putty and SSH into the iPhone by typing the iPhone IP address, root as username and alpine as password.
5. 
Navigate to /var/mobile/Applications/ folder and identify the CardInfo application directory using ‘find . –name CardInfo’ command. On my iPhone CardInfo application is installed on the – /var/mobile/Application/B02A125C-B97E-4207-911B-C136B1A08687/ directory. 

cardinfo directory

6. Navigate to the /var/mobile/Application/B02A125C-B97E-4207-911B-C136B1A08687/CardInfo.app directory and notice CARDDATABASE.sqlite3 database file.

cardinfo sqlite file

7. Using sqlite3 command, view the CARDDATABASE.sqlite3 and notice that CARDINFO table is empty.

Note: Sqlite files can also be copied from the iPhone to a workstation over SSH and viewed using Sqlite data browser & Sqlite spy tools.

cardinfo sqlite before login

8. On the iPhone, open CardInfo application and login (works for any username and password).

cardinfo login

9.Enter credit card details and click on Save button. In the background, it saves the card details in the Sqlite database.

cardinfo - card details                    cardinfo - saved details

10. View CARDDATABASE.sqlite3 and notice that CARDINFO table contains the credit card details data.

cardinfo sqlite after save

11. Logout from the application on the iPhone. In the background, it deletes the data from the Sqlite database.

cardinfo logout

12. Now view CARDDATABASE.sqlite3 and notice that CARDINFO table is empty.

cardinfo sqlite after logout

Steps to recover the deleted data from CardInfo Sqlite file:

Sqlite database engine writes the data into Write Ahead Log before storing it in the actual database file, to recover from system failures. Upon every checkpoint or commit, the data in the WAL is written into the database file. So if an entry is deleted from the Sqlite database and there is no immediate commit query, we can easily recover the deleted data by reading the WAL. In case of iOS, strings command can be used to print the deleted data from a Sqlite file. In our case, running ‘strings CARDDATABASE.sqlite3’ command prints the deleted card details.

cardinfo sqlite recovered

In iOS, if an application uses the Sqlite database for temporary storage, there is always a possibility to recover the deleted temporary data from the database file.

For better security, use custom encryption while storing the sensitive data in Sqlite database. Also, before deleting a Sqlite record, overwrite that entry with junk data. So even if someone tries to recover the deleted data from the Sqlite file, they will not get the actual data. Use iOS data protection constants while creating the Sqlite files.

Cookies.binarycookies

Most of the iOS applications do not want to prompt the user for login everytime. So they create persistent cookies and store them in cookies.binarycookies file on the application’s home directory.  During penetration test, investigate the cookies.binarycookies file for sensitive information and to find session mangement issues. Cookies.binarycookies is a binary file and the content is not in readable format. So I wrote a python script BinaryCookieReader.py that can read the cookie file and display the content on the screen.

Steps to read the Cookies.binarycookies:

1. On Windows, download WinScp, Python & BinaryCookieReader.py.
2. 
Connect the iPhone and the workstation to the same Wi-Fi network.
3. 
Run WinScp and SSH into the iPhone by typing the iPhone IP address, root as username and alpine as password.
4. 
Navigate to the Library/Cookies folder in the application’s home directory.
5.
Copy the Cookies.binarycookies file to the windows machine by dragging it.

Cookies-Binarycookies-File

6. On windows, open command prompt and run the below command to list the contents of cookies.binarycookies file.

Python BinaryCookieReader.py [Cookies.binarycookies file path]

Below is the screenshot of cookies created by Facebook iOS Application.

facebook iOS cookie file

Keyboard Cache

In an effort to learn how user’s type, iOS devices utilize a feature called Auto Correction to populate a local keyboard cache on the device. The keyboard cache is designed to autocomplete the predictive common words. The problem with this feature is, it records everything that a user types in text fields. The cache keeps a list of approximately 600 words. The keyboard cache is located at Library/Keyboard/en_GB-dynamic-text.dat file. To view the Keyboard cache, copy the en_GB-dynamic-text.dat file to a computer over SSH and open the file using a Hex Editor. Below is the screenshot of a keyboard cache Hex view.

iOS keyboard cache

Keyboard Cache does not store the informtion typed in the fields which are marked as Secure. By default, passwords and strings with all digits (pins & credit cards) are marked as Secure. Hence the data typed in those fields does not store in the keyboard cache. But data typed in other text fields like username, security questions & answers might get stored in the keyboard cache. During a pentest clear the existing keyboard cache by navigating to iPhone Settings -> General -> Reset -> Reset Keyboard Dictionary (shown in the below image), then browse the application & enter data in text fields and anlyze whether the data is getting stored in the keyboard cache or not.

Clear iOS keyboard cache

During the application development, to disable auto complete for a text field, either mark it as secure (ex: mytextField.secureTextEntry = YES) or disable the autocomplete (mytextField.autocorrectionType = UITextAutocorrectionTypeNo;).

Along with the keyboard cache, when a user copies data from a textfield, iOS stores the data into a pasteboard (clipboard in other operating systems). The pasteboard is shared among all the application, so the information copied in one application can be accessed from other application by reading the pasteboard. If the application is dealing with senstive data, it is recommended to use private or application specific pasteboard.

Snapshot Storage

Pressing the iPhone home button shrinks the iOS application and moves it to the background with a nice effect. To create that shrinking effect, iOS takes a screenshot of the application and stores it in the Library/Caches/Snapshots folder in the respective application’s home directory. This might result in storing the user’s sensitive information on the device without user’s knowledge. Snapshots stored on the iPhone will automatically cleared after the device is rebooted.

Ex: Incase of Gmail iOS application, when a user press the iPhone home button after viewing the email, a snapshot of users’ email gets stored on the device without user’s knowledge. Below snapshot is captured after viewing a mail from the Citibank.

Gmail iOS App Snapshot Storage

During development, the application snapshot problem can be fixed in two ways.
1. Remove sensitive data or change the screen to blank before the applicationDidEnterBackground()
function returns.
2. Instead of hiding or removing sensitive data, application’s back grounding can be disabled altogether by setting the “Application does not run in background” property in the application’s Info.plist file.

File Cache

Along with plist files, sqlite files, binary cookies & snapshots, iOS applications can store other format files like pdf, xls, txt, etc. when viewed from the application. For example, in Yandex.Mail iPhone application, when a user views an attachment it gets stored on the device and remains on the device even after user logged out from the mail application. Applications which are storing temp files on the device, should clear those files upon logout/close for better security.  Below is the screenshot of Yandex.Mail attachement directory.

iOS Yandex Mail Attachement Storage

Error Logs

In general, iOS applications write data into logs for diagnostic and troubleshooting purpose. Also, during development, applictions developers commonly use NSLog for debugging purpose. These logs might include requests, responses, cookies, authentication tokens and other sensitive data. On the iPhone, data passed to the NSLog funciton is logged by Apple System Log (ASL) and the data remains on the log until the device is rebooted. Also, Error logs are not bounded by the application sandbox. Which means, error log generated by one application can read by other application. So if an application logs sensitive data, a malicious application can actively query for this data and send it to a remote server.

Error logs on the iPhone can be viewed directly using Console app. Console app is available in AppStore. Error logs can also be viewed using iPhone configuration utility or by syncing the device with iTunes and looking at CrashReporter folder.

For this exercise, I have created a demo application called CardInfoDemo. CardInfoDemo is a self signed application, so it can only be installed on a Jailbroken iPhone. The CardInfo demo application accepts any username & password, then collects the credit card details from the user and writes it into the error log.

Steps to view the error logs:

1. Install CardInfoDemo application on the iPhone.
2. On windows, install & open the iPhone Configuration Utility.
3. 
Connect the iPhone to the windows machine using USB cable. Notice that the connected device is listed in the iPhone configuration utility. Select the device and navigate to Console tab.
4. 
On the iPhone, open CardInfo application and login (works for any username and password).
5. 
Enter credit card details and click on Save button. In the background, it logs the card details.

CardInfoDemo iOS App

6. On the iPhone configuration utility console tab, you can notice the card details logged by the CardInfoDemo application.

iOS App Error log

For better security, do not log sensitive data. Also, remove debugging and troubleshooting logs from the application before publishing it.

Penetration Testing iPhone Applications is going to be covered in a series of articles. Below are the links for next articles. 

Part 5runtime analysis of iOS Applications.

References:

1. Debunking NSLog Misconceptions
http://blog.gdssecurity.com/labs/2012/3/28/debunking-nslog-misconceptions.html
2. What’s in your iOS Image Cache ?
http://software-security.sans.org/blog/2011/01/14/whats-in-your-ios-image-cache-backgrounding-snapshot
3. Hacking and Securing iOS Applications by Jonathan Zdziarski

 
 

Recovering data from the iPhone corrupted backups

01 Apr

At times when iTunes couldn’t finish the backup process (USB cable disconnect during backup/iOS upgrade, Power failure during backup), the backup gets corrupted and remains unreadable. As the corrupted backup does not contain meta files like Manifest.plist & Manifest.mbdb, it is not possible to restore the backup onto the iPhone and it is also not possible to read the backup using backup reader software like iPhone backup browser & iPhone backup extractor. So I wrote a python script iOS-corrupted-backup-reader.py that can read & recover data from the corrupted backups. Usage of the script is listed below.

Steps to use iOS-corrupted-backup-reader.py (Windows):

1. On windows, install Python 2.6.
2. Download iOS-Corrupted-Backup-Reader.py and place it in C:\ drive.
3. Create two folders backup & output in C drive.
4. From the iOS backup directory C:\Users\[user-name]\AppData\Roaming\Apple Computer\MobileSync\Backup\[iPhone-UDID]\,  copy all the files and place them in C:\backup directory.
5. Open  the command prompt, navigate to C:\ drive and type the below command.

\Python26\python.exe iOS-Corrupted-Backup-Reader.py c:\backup c:\output

6. It converts the backup files into readable format and places them in C:\output directory.

Steps to use iOS-corrupted-backup-reader.py (Mac OS X):

1. Create two folders backup & output on Desktop.
2. Download iOS-Corrupted-Backup-Reader.py and place it on Desktop.
3. From the iOS backup directory ~/Library/Application Support/MobileSync/Backup/[UDID], copy all the files and place them in backup directory.
4. Open the terminal and run the below command.

Python iOS-Corrupted-Backup-Reader.py ~/Desktop/backup/ ~/Desktop/output/

5. It converts the backup files into readable format and places them in output directory.

The script extracts and structures all the default files like Contacts, SMS, Calendar, etc. into directories with actual file names. Other third party application files are converted into readable format and gets stored in other-data folder in output directory without actual file names. Manifest.mbdb file maps the actual filenames to backup filenames and the mbdb file is not available in the case of corrupted backups. So it is not possible to get the exact file names. In general, most of the iOS applications store the data in plist, sqlite and Jpeg format. You can use plist editor sqlite spy and image viewers to open the files and read the data manually.

Note: Data recovery is only possible in the case of normal backups. If the backup is encrypted (encrypt backup option is checked in iTunes), it is not possible to read & recover the data from the corrupted backups.

 
 

iOS – Sqlite3 command killed:9 problem

29 Mar

Executing commands on a Jailbroken iPhone (>iPhone 4), might suddenly fail and display killed:9 error. In that case, follow the below steps to resolve the problem.

Steps listed below explains how I fixed the Sqlite3 command killed: 9 error. The same technique works for other binaries and commands too.

Steps:
1. Create a self signed code signing certificate.

On Mac OS X, go to Keychain Access -> Certificate Assistant -> Create a Certificate. It opens the certificate assistant window. Enter name (in my case it is securitylearn.net) and select certificate type as Code signing. Check let me override defaults option. Hit continue until it creates the certificate.

OS X self signed certificate

After creation of the certificate, the keychain looks as shown in the image below.

Certificate in keychain1

2. Connect to the iPhone over SSH using Cyberduck.
3. Copy the sqlite3 executable located at /usr/bin from the iPhone to Mac.
3. Open Mac terminal and run the below command to sign the sqilte3 with self signed certificate.

Codesign -fs securitylearn.net sqlite3

4. Replace the sqlite3 executable on the iPhone with newly signed sqlite3.
5. Now executing sqlite3 command works without any errors.

 
 

The Paraben’s iRecovery Stick Review

21 Mar

The Paraben’s iRecovery Stick is an USB flash drive designed to recover deleted data from the Apple iOS devices like iPhone, iPad & iPod touch. The product allows the investigators to recover data either directly from the device or from the iTunes back-up files. It is designed to support all iOS versions ranging from 1.x to 6.x and it works with iPhone 3GS, 4, 4S, 5 & other iOS devices. The iRecovery stick will not only recover the deleted data, it also downloads all the contents of the device. The article explains the usage of iRecovery stick and covers the pros and cons of it.

iRecovery stick features:

  • Downloads phone contents – downloads all the user data like photos, contacts, calendar, etc.
  • Recovers deleted data – recovers deleted text messages, contacts, call history, etc.
  • Easy to use – simply connect the iPhone and the iRecovery stick to the computer, then click the start button in the recovery software.
  • Portable – It is an USB thumb device and easy to carry.
  • Inconspicuous – It resembles a commonly used USB thumb drive, so it can be used as a spy device and no one would suspect that the device is used to recover data from the iPhone.
  • Works on backup files – recovers data from iTunes backup files.

 

Setup:

The iRecovery stick shipment box contains the iRecovery stick and an USB cable that is compatible with the iPhone 3GS, 4 & 4S. The iRecovery stick is compatible with Windows XP & 7 and provides an easy-to-use user interface. iRecovery stick does not support vmware/virtualbox environment and Linux & Mac OS X operating systems. Also, it is mandatory to turn off the antivirus software running on the Wndows OS for better data recovery. The iRecovery Stick is a portable and a simple to use USB flash drive which contains the recovery software – iRecoveryStick.exe. Recovery software included in the iRecovery stick can be installed on to the hard drive or it can be executed directly from the USB drive. Below image displays the contents of iRecovery stick USB drive.

iRecovery stick USB drive

Installation of the iRecovery software is well documented in the iRecovery Getting Started manual located in the USB flash drive.

Data acquistion and Recovery from the device:

The iRecovery Stick is very simple to use. Simply connect the iPhone to a Windows based computer with the USB cable and then connect the iRecovery stick to the same computer throuh an USB port. Once the two devices are connected, run the iRecoveryStick.exe program. Welcome screen of the iRecovery stick software is shown in the below image.

iRecovery stick device recovery

Once open, click on start recovery button (highlighted in the above image). Then the recovery software prompts to choose connected device as shown in the image below.

iRecovery stick connected device

Click on the device to start the recovery process (shown in the below image). The data recovery process will take several minutes to few hours to complete based on the size of the iPhone disk. During a test on Intel i5 2nd generation processor laptop it took 14 minutes to recover 256MB data from the iPhone 4.

iRecovery stick data recovery

The recovery process acquires existing data and recovers deleted data from the iPhone, but the majority of the data will be normal user’s data which has never been deleted. Once the recovery process is completed, then it immediately displays all the data recovered from the iPhone (shown in the below image). The recovery process downloads the existing contents of the phone such as contacts, call history, text messages, calendars, notes, pictures, multimedia and all other user’s data like safari history, safari bookmarks, GPS history & application cookies. It also recvovers different types of deleted data including text messages, contacts, call history, and calendar entries. The iRecovery stick is not capable of carving the file system, so it can only recover the deleted data from the Sqlite database files and does not recover the deleted files from the file system, i.e it does not recover the deleted photos.

iRecovery stick recovered data

The user interface also provides an option to generate easily readable report or to export the recovered data to Excel sheets. During a test, export to Excel option took more time than the actual recovery process.

iRecovery stick export to excel

The iRecovery stick does not have the capability to bypass the iPhone passcode. So if the device is protected with a passcode, unlock it before connecting it to the computer for recovery.

Data acquisition and Recovery from the backup:

The iRecovery Stick can also recover data from the iTunes backups. In general, iTunes backup contains a copy of everything on the device like contacts, SMS, photos, calendar, music, call history, notes, network settings, safari bookmarks, cookies and application data, etc. So the iRecovery stick recovers the same types of data it recovers from the iPhone itself. To recover data from the backups, run iRecoveryStick.exe and load the iTunes backup files created in Windows. Welcome screen of the iRecovery stick software is shown in the below image.

iRecovery stick backup recovery

Click on start import from iTunes backup button (highlighted in the above image). Then the recovery software prompts to choose specific iOS version as shown in the image below.

iRecovery stick backup recovery-1

Clicking on the specific iOS version prompts the user to open the existing iTunes backup as shown in the image below. In general iTunes backup gets stored in the below locations.

Windows XP – C:\Documents and Settings\[user name]\Application Data\Apple Computer\MobileSync\Backup\

Windows 7 – C:\Users\[user name]\AppData\Roaming\Apple Computer\MobileSync\Backup\

iRecovery stick open backup

Once the backup is selected, then the recovery process gets started. The data recovery process will take several minutes to few hours to complete based on the size of the backup files. During a test on Intel i5 2nd generation processor laptop it took 15 minutes to recover 300MB data from the iTunes backup.

Once the recovery process is completed, then it immediately displays all the data recovered from the backup files. The recovery process extracts the existing contents from the backup such as contacts, call history, text messages, pictures, multimedia and all other user data like user’s internet browsing history & application cookies. It also recvovers different types of deleted data from the backup including text messages, contacts, call history, calendar entries and notes.

The iRecovery stick can only recover data from the iTunes normal backups and it does not work with the iTunes encrypted backups.

What data is recovered:

Once the recovery process is completed, iRecoveryStick displays the recovered data in an easy readable format as shown in the image below.

iRecovery stick recovered data

The recovery process recovers the below existing data from the device/backup:

  • Messages – sent/received SMS messages including the exact date and time.
  • Contacts – phonebook data with creation and modification dates.
  • Call history – call logs including the exact duration time.
  • Graphics – photos & thumbnail images.
  • Organizer – calendar & notes.
  • Multimedia – mp3 files & recorded videos.
  • Internet data – safari history, safari bookmarks, safari suspend state, safari cookies, email accounts, youtbue bookmarks and application cookies.
  • Tracking history – geographical locations. It contains longitude and latitude coordinates along with a timestamp and is displayed in the Google Earth viewer.
  • Other data – this data includes maps history, maps bookmarks, maps directions and other properties.

 

The recovery process recovers the below deleted data from the device/backup:

  • Recovered data
    • Contacts
    • SMS
    • iMessages
    • Notes
    • Call history
    • Calendar data
    • Internet data
    • Tracking history

 

The iRecovery stick does not recover data from the iOS keychain file. Also, it does not recover the deleted files & photos.

Conclusion:

The iRecovery stick is a simple to use tool for data recovery from iOS devices. It recovers most of the data from the device, however it does not recover deleted files from the file system. Due to this limitation it may not be a great tool for forensic investigators. However this is the perfect device for employees, parents, spouses, boyfriends & girlfriends who wants to spy or recover the deleted SMS, contacts, call history and web history from iOS devices.

The paraben’s iRecovery stick costs around 200$. So in my personal opinion, I feel it is worth for money.

 
 

NESSUS Vulnerability Scanner – Basics

27 Feb

If you are looking for a vulnerability scanner, you might have came across several expensive commercial products and tools, with wide range of features and benefits. If a full featured free vulnerability scanner is on your mind, then it’s time to know about Nessus. The article covers installation, configuring and select policies, starting a scan, analyzing the reports using NESSUS Vulnerability Scanner.

Nessus was founded by Renuad Deraison in the year 1998 to provide to the Internet community a free remote security scanner. It is one of the full fledged vulnerability scanners which allow you to detect potential vulnerabilities in the systems. Nessus is the world’s most popular vulnerability scanning tool and supported by most of the research teams around the world.

The tool is free of cost and non-commercial for non-enterprises.  Nessus uses web interface to set up, scan and view repots. It has one of the largest vulnerability knowledge bases and because of this KB the tool is very popular.

Nessus supports wide range of operating systems that include Windows XP/7, Linux, Mac OS X, Sun Solaris, etc.

Key Features:

  • Identifies Vulnerabilities that allow a remote attacker to access sensitive information from the system.
  • Checks whether the systems in the network has the latest software patches.
  • Tries with Default passwords, common passwords, on systems account
  • Configuration audits.
  • Vulnerability analysis.
  • Mobile Device audits.
  • Customized reporting.

Installation & Configuration:

  1. You can download the Nessus home feed (free) or professional feed from Nessus website.
  2. Once you download the Nessus home tool, you need to register for generating an activation key.  The activation key will be sent to your email id. 
  3. Install the tool (Installation of nessus tool will be quite confusing and the installation guide comes handy).
  4. Open the Nessus in the browser, normally it runs on the port 8834 -
    http://localhost:8834/WelcomeToNessus-Install/welcome and follow the screen.
  5. Create an account with Nessus. 
  6. Enter the activation code you have obtained by registering with the Nessus website. Also you can configure the proxy if needed by giving proxy hostname, proxy username and password.
  7. Then scanner gets registered and creates the user account.
  8. Then downloads the necessary plugins (It takes some time for downloading the plugins). 
  9. Once the plug-ins are downloaded then it will automatically redirects you to a login screen. Provide the Username and password that you have created earlier to login.
     

Running the Tool:

Nessus gives you lots of choices when it comes to running the actual vulnerability scan. You’ll be able to scan individual computers, ranges of IP addresses or complete subnets. There are over 1200 vulnerability plugins with Nessus using which you’ll be able to specify individual or set of vulnerabilities to test for. In contrast to other tools Nessus won’t assume for explicit services running on common ports instead it will try to exploit the vulnerabilities.

One of the foundations for discovering the vulnerabilities in the network are:

  • Knowing which systems exist
  • Knowing which ports are open and which listening services are available in those ports
  • Determining which Operating System is running in the remote machine

Once you log into the Nessus using web-interface, you will be able to see different options like,

  • Policies –Using which you can configure the options required for scan
  • Scans -for adding different scans
  • Reports -for analyzing the results
     

Basic workflow of Nessus tool is to Login, Create or Configure the Policy, Run the Scan and Analyze the Results.

POLICIES:

Policies are nothing but the vulnerability tests that you can perform on the target machine. By default Nessus has 4 policies.

Nessus policies

Above figure shows the default polices that comes with Nessus tool.

External Network Scan:

The policy is pre-configured in such a way that Nessus scans externally facing hosts, which provides services to the host. It scans all 65,535 ports of the target machine. It is also configured with Plugins required for web application vulnerabilities tests like XSS.

Internal Network Scan:

This policy is configured to scan large internal networks with many hosts, services, embedded systems like printers, etc… This policy scans only standard ports instead of scanning all 65,535 ports.

Web App Tests:

Nessus uses this policy to detect different types of vulnerabilities exist in the web applications. It has the capability to spider the entire web site and discovers the content and links in the application. Once the spider process has been completed then Nessus starts to discover the vulnerabilities that exist in the application.

Prepare for PCI DSS audits:

This policy consists of PCI DSS (Payment Card Industry Data Security Standards) enabled. Nessus compares the results with the standards and produces a report for the scan. The scan doesn’t guarantee for a secure infrastructure.  Industries or Organizations preparing for PCI-DSS can use this policy to prepare their network and systems.

Apart from these pre-configured policies you can also upload a policy by clicking on “Upload” or configure your own policy as per your scan requirement by clicking on “New Policy”.

Configuring the Policy:

  • Click on the policies tab on the top of the screen
  • Click on the New Policy button to create a new policy

Under the General settings tab select the “setting type” based on scan requirement, like Port Scanning, Performance scanning etc… Based on the type Nessus prompts different options that has to be filled. For example ‘Port Scanning’ has the following options

Nessus Port scanning options

Above figure shows configuring options of Port Scanning.

Enter the port scan range. By default Nessus scans all the TCP ports in /etc/services file. You can limit the ports by specifying it manually (like 20-30). You have different scanners like Nessus SNMP scanner, SSH scanner, ping remote host, TCP Scanner, SYN scanner, etc…. Enable by selecting the check box as per the scan requirement.

  • Enter the credentials for scan to use. You can use single set of credentials or multiple set of credentials if you have. You can also work it out without entering the credentials.
  • The plugins tab has number of plugins. By default Nessus will have all the plugins enabled. You can enable or disable all the plugins at a time or enable few from the plug-in family as per the scan you’d like to perform. You can also disable some unwanted plugins from the plug-in family by clicking on particular plug-in.

Nessus sub plugins

The above figure shows the sub-plugins for the plugin Backdoors.

In the above Figure the green one shows the parent plugin and the blue once shows the sub-plugins or the plugins under the plugin (backdoor). You can enable or disable by simply clicking on the enabled button.

  • In the Preferences, you are provided with a drop down box to select different types of plugins. Select the plugin based on the scan requirement and specify the settings as per the plugins requirement. Click finish once completed. For example: configure the database.

Nessus database settings plugin

The above figure shows the configuration of Database settings plugin.

SCANS:

Once you are done with configuring the policies as per your scan requirement, you need to configure the scan details properly. You can do it under Scan tab.

Under the Scan tab, you can create a new scan by clicking New Scan on the top right.  Then a pop up appears where you need to enter the details like Scan Name,  Scan Type, Scan Policy & Target.

  • Scan Name: The name that you are willing to give to the scan.
  • Scan Type:  You have options to RUN the scan instantly by selecting RUN NOW. Or you can make a template which you can launch later when you are willing to run. All the templates are moved under the TEMPLATE tab beside the SCAN tab.
  • Scan Policy: Select the policy that you have configured previous in the policies section.
  • Select Target: Enter the target machine which you are planning to test. Depending upon the targets Nessus takes time to scan the targets.
     

Results:

Once the scanning process has been completed successfully, results can be analyzed from RESULTS menu.

  • Once the scan has been completed, you can see the name of the scan under the results section. Click on the name to see the report.
  • Hosts: Specifies all the target systems that you have scanned.
  • Vulnerabilities: Displays all the vulnerabilities on the target machine that has been tested.
  • Export Results: You can export the results into difference formats like html, pdf, etc…  You can also select an individual section or complete result to export based on your requirement.

Let us try out an example now-

I have configured a policy named Basic Scan. We have many options while configuring or building the policy like port scanners, performance of the tool, Advanced etc.

Nessus port scanning settings for basic scan

The above figure shows configuration settings of Port Scanning for the policy Basic Scan.

You don’t need credentials now, so skip the credentials tab and move to Plugins tab. You need to configure the specific plug-in as per the scan requirement that you are willing to perform on remote machine.

Nessus plugins for basic scan

The above figure shows the plugins that I have enabled for the policy Basic Scan. I have enabled few plugins for windows machine scan.

Nessus scan configuration

The above figure shows the configuration of the Scan.

I have configured the scan to run instantly with the policy that I have created earlier. And the scan target specify the IP address I am willing to scan.

Once all the details has been entered click on Create Scan which shows the Scan is running as shown in the below Figure.

Nessus running scan

Once the scanning has been completed then you can see the results in Results tab. Below Figure shows the same.

Nessus results

Double clicking on the title displays the scan results.

Nessus scan result

The above figure shows the Hosts details. It includes all the targets that you have scanned during the test. Double clicking on the host address displays the vulnerabilities Nessus have identified during the test. You can also click on Vulnerabilities tab to check out the vulnerabilities.

Nessus vulnerabilities menu

The above figure shows the Vulnerabilities that Nessus found during its scan. Based on the Risk Nessus marks it as high, medium, info etc… Clicking on the Vulnerability gives you brief description of it.

For example let us go with Netstat portscanner, displays you the following information

Nessus port scan result

The above figure shows the ports opened in the target machine.

In the same manner you can analyze complete details by clicking on the vulnerabilities. Nessus also suggests the solutions or remedies for the vulnerabilities with few references.

Conclusion:

Nessus is a tool which automates the process of scanning the network and web applications for the vulnerabilities also suggests solutions for the vulnerabilities that are identified during the scan.

 
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Posted by kamalb

 
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