NIST is publishing a regularly updated set of CDs with hashes for a number of software packages. The "National Software Reference Library" (NSRL) [1] is frequently used for forensics to eliminate unaltered standard files from an investigation. However, I feel that this database also has a lot of use for malware analysis. Anti-malware software usually takes an "enumerate badness" approach in attempting to come up with signatures for all known malware. With the current flood of new malware variants, this approach does not work well anymore.

One problem with the NIST NSRL was that there was no easy way to look up a single hash or file. You could order the CD set or download them, but there was no simple way to just lookup just one hash which is particular useful for malware analysis. Not anymore. We downloaded the database for you, and it is now available to be queried here: http://isc.sans.org/tools/hashsearch.html .

The plan is to add our own hash collections to it. I may also offer a DNS based lookup if there is interest. In order to provide some malware information, I added a lookup against the Team Cymru malware hash database.

How to use this tool

You may search based on filename, sha1 hash or md5 hash. The malware lookup only works for md5 hashes right now. For each search, you may get more then one result back. For example, if you search for "cmd.exe", you will get hashes back for various versions of Windows which include cmd.exe. Same if you enter a hash, and the same binary was used in multiple products.

If you would like to contribute your own hash collection, please let us know. In particular if you have a good Windows 7 hash collection. As the focus of this tool is malware analysis, hashes of executables and libraries are most appreciated. Please contact us via http://isc.sans.org/contact.html to discuss details. Hashes contributed by sources other then NIST will be marked clearly as they may not live up to the exacting standards of NIST.

[1] http://www.nsrl.nist.gov/
[2] http://www.team-cymru.org/Services/MHR/

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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