Re: .exe

[Jeff Kell <jeff-kell () utc edu>]

On 5/5/2013 1:51 AM, Caleb Jaren wrote:
> Try flow:from_server,established; and instead of the string ".exe" try
> content:"|4d 5a|"; which is equivalent to the text string "MZ" found
> at the beginning of most PE files.

And based on that alone, on any random data stream matching on two bytes
"4d 5a" you're going to get a hit every 64K data packets.  If you're
including SSL/TLS/VPN/etc encrypted traffic you're going to hit.

It's one thing to create a signature to detect a "known thing".  It's
another thing entirely to reduce or eliminate false positives.

The former will gain you points on the "canned" IDS/IPS test suites. 
The latter will gain you points in the real world.

Jeff

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