In several forensic investigation cases, Kivu has analyzed iOS backup files as a method of obtaining evidence of text messages or other data from an iOS device, usually when an iOS device is not readily available or as a means of cross-correlating evidence.

These backups are often made to the custodian’s computer when they connect their iOS device to a computer to charge it or sync it with iTunes. When they connect their iPod touch, iPhone, or iPad to their computer, certain files and settings on their device are automatically backed up. As such, they are locally stored on the custodian’s computer and can be extracted and parsed for further analysis.

In a recent case, the backups were extracted from the custodian’s laptop, which was provided to Kivu. The backups pertained to two iPhone devices. Kivu forensically extracted the backups from the custodian’s laptop and was able to parse the backups and uncover text message data that came from both the custodian’s current iPhone and the prior one, which was no longer in her possession.

Here’s how the text messages were retrieved

 

Within the “Backup” directory under MobileSync, there is a subdirectory named for the unique device identifier (UDID) of the device for a full backup. The UDID is a 40-character hexadecimal string that identifies the device [example: 5b8791c14e926cc9220073aefcedd2b831c843b1]. Sometimes, the UDID will have a timestamp appended to it that indicates the date and time that the backup was made. For example, a directory named 5b8791c14e926cc9220073aefcedd2b831c843b1-20150506 122733 indicates that the iOS device was backed up on May 6, 2015 at 12:27:33 PM.

Within the UDID directory, there are numerous files with a similar naming convention as the UDID directory without a file extension. These filenames are actually SHA1 hash values of files from the device. When backing up an iOS device through iTunes, iTunes computes a SHA1 hash value of the file’s path. Below is a chart detailing several common SHA1 file names for files pulled from an iOS in the course of an iTunes backup.

Since text messages are often of interest, it’s important to note the SHA1 hash value assigned to sms.db. This is the database file that holds text message data, including sender, recipient, and content of messages.

 

Sources:

http://ios-forensics.blogspot.com/2014/07/apple-ios-backup-file-structure.html
http://resources.infosecinstitute.com/ios-5-backups-part-1/
http://www.iphonebackupextractor.com/blog/2012/apr/23/what-are-all-files-iphone-backup/

About Kivu

Kivu is a nationally recognized leader for security assessments and breach response services.  For more information about collecting forensic data from Apple devices, please contact Kivu.

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