|This article needs additional citations for verification. (April 2011)|
|Stable release||6.14 / July 30, 2013|
|License||GPL (free software)|
PhotoRec is a free and open source file carver data recovery software tool designed to recover lost files from digital camera memory (CompactFlash, Memory Stick, Secure Digital, SmartMedia, Microdrive, MMC, USB flash drives, etc.), hard disks and CD-ROMs. It recovers most common photo formats, including JPEG, and also recovers audio files including MP3, document formats such as OpenDocument, Microsoft Office, PDF and HTML, and archive formats including ZIP. 
PhotoRec does not attempt to write to the damaged media the user is about to recover from. Recovered files are instead written to the directory from which PhotoRec is run, any other directory may be chosen. It can be used for data recovery or in a digital forensics context. PhotoRec is shipped with TestDisk.
PhotoRec is compatible with:
- DOS (either real or in a Windows 9x DOS box)
- Microsoft Windows: NT4, 2000, XP, 2003, 2008, Vista, Windows 7
- FreeBSD, NetBSD, OpenBSD
- Mac OS X
How PhotoRec works
FAT, NTFS, ext2/ext3/ext4 filesystems store files in data blocks (also called data clusters under Windows). The cluster or block size remains at a constant number of sectors after being initialized during the formatting of the filesystem. In general, most operating systems try to store the data in a contiguous way so as to minimize data fragmentation. The seek time of mechanical drives is significant for writing and reading data to/from a hard disk, so that′s why it′s important to keep the fragmentation to a minimum level.
When a file is deleted, the meta-information about this file (filename, date/time, size, location of the first data block/cluster, etc.) is lost; e.g., in an ext3/ext4 filesystem, the names of deleted files are still present, but the location of the first data block is removed. This means the data is still present on the filesystem, but only until some or all of it is overwritten by new file data.
To recover these ‘lost’ files, PhotoRec first tries to find the data block (or cluster) size. If the filesystem is not corrupted, this value can be read from the superblock (ext2/ext3/ext4) or volume boot record (FAT, NTFS). Otherwise, PhotoRec reads the media, sector by sector, searching for the first ten files, from which it calculates the block/cluster size from their locations. Once this block size is known, PhotoRec reads the media block by block (or cluster by cluster). Each block is checked against a signature database; which comes with the program and has been growing in the type of files it can recover ever since PhotoRec′s first version came out. It′s a common data recovery method called File carving.
For example, PhotoRec identifies a JPEG file when a block begins with:
- Start Of Image + APP0: 0xff, 0xd8, 0xff, 0xe0
- Start Of Image + APP1: 0xff, 0xd8, 0xff, 0xe1
- or Start Of Image + Comment: 0xff, 0xd8, 0xff, 0xfe
If PhotoRec has already started to recover a file, it stops its recovery, checks the consistency of the file when possible and starts to save the new file (which it determined from the signature it found).
If the data is not fragmented, the recovered file should be either identical; or possibly larger than the original file, in size. In some cases, PhotoRec can learn the original filesize from the file header, so the recovered file is truncated to the correct size. If, however, the recovered file ends up being smaller than its header specifies, it is discarded. Some files, such as *.MP3 types, are data streams. In this case, PhotoRec parses the recovered data, then stops the recovery when the stream ends.
When a file is recovered successfully, PhotoRec checks the previous data blocks to see if a file signature was found but the file wasn′t able to be successfully recovered (i.e., the file was too small), and it tries again. This way, some fragmented files can be successfully recovered.
PhotoRec and TestDisk have been downloaded more than 150,000 times in July 2008 from the primary website. In fact these utilities are even more popular as they can be found on various GNU/Linux Live CDs:[original research?]
- Recovery Is Possible 
- Knoppix STD 
- GParted Live CD 
- Parted Magic 
- Slax-LFI, a Slax-derived distribution 
- SystemRescueCD 
- Trinity Rescue Kit 
- Ubuntu Rescue Remix, an Ubuntu derivation 
They are also packaged for numerous GNU/Linux based distributions:
- ALT Linux
- ArchLinux Extra Repository
- Debian contrib
- Fedora Extras
- Red Hat Epel
- FreeBSD ports
- Gentoo and Gentoo Portage
- Mandriva contrib
- PLD Linux Distribution
- Source Mage GNU/Linux
- File Formats Recovered By PhotoRec
- Jack Wiles, Kevin Cardwell, Anthony Reyes (2007). The best damn cybercrime and digital forensics book period, p. 220. Syngress Publishing Inc. ISBN 978-1-59749-228-7.
- Cameron H. Malin, Eoghan Casey, James M. Aquilina (2008). Malware Forensics: Investigating and Analyzing Malicious Code, p. xxviii. Syngress Publishing Inc. ISBN 978-1-59749-268-3.
- Nathan Clarke (2010), Computer Forensics: A Pocket Guide, p. 67. IT Governance Publishing. ISBN 978-1-84928-039-6.
- Scott Mueller, Brian Knittel (2008). Upgrading and Repairing Microsoft Windows, Second Edition, page 685. Pearson Education Inc. ISBN 978-0-7897-3695-6.
- "PhotoRec - CGSecurity". Retrieved 1/3/2013.
- How PhotoRec works (Description from the author website)
- "Recovery Is Possible Changelog". Retrieved 1/3/2013.
- "Knoppix STD: Tools". Retrieved 1/3/2013.
- "GParted -- Live CD/USB/PXE/HD". Retrieved 1/3/2013.
- "programs – Parted Magic". Retrieved 1/3/2013.
- "Recover file with PhotoRec". Retrieved 1/3/2013.
- "System-tools - SystemRescueCd". Retrieved 1/3/2013.
- "6. List of all commands". Retrieved 1/3/2013.
- "Software Ubuntu Rescue Remix". Retrieved 1/3/2013.
- TestDisk on ALT Linux
- ArchLinux Extra Repository
- TestDisk on Debian
- TestDisk in Fedora
- "RepoView: "Fedora EPEL 6 - x86_64"". Retrieved 27 July 2013.
- TestDisk in FreeBSD ports
- TestDisk in Gentoo
- TestDisk in Gentoo Portage
- TestDisk in Source Mage
- TestDisk in Ubuntu
- Official site
- Adrian Crenshaw, Data Carving with PhotoRec to retrieve deleted files from formatted drives for forensics and disaster recovery. This video introduces the concept of data carving/file carving for recovering deleted files, even after a drive has been formatted.
- Seth Fogie - InformIT, Stealing Your Family Vacation: Memories of a Media Card
- Kaspersky Lab, Recovering files encrypted by Virus.Win32.Gpcode.ak using PhotoRec After encrypting files, the virus deletes the original files but PhotoRec can recover them.