[Snort-sigs] False positive - sid 1365
smil at ...1754...
Fri Mar 18 11:24:18 EST 2005
On Fri, 18 Mar 2005, Paul Schmehl wrote:
> /usr/local/share/snort/web-attacks.rules:alert tcp $EXTERNAL_NET any ->
> $HTTP_SERVERS $HTTP_PORTS (msg:"WEB-ATTACKS rm command attempt";
> flow:to_server,established; content:"rm%20"; nocase;
> classtype:web-application-attack; sid:1365; rev:5;)
> We get a ton of fps on this signature. I'm wondering why the content isn't
So do I, yet...
> "%20rm%20" instead of "rm%20". Wouldn't you need a space on either side for
> the command to be parsed/understood?
"%20rm%20" will not catch attempts ala "somescript.cgi?rm%20/etc/passwd"
I had seen attempts like that in the past (although the script in
question was not vulnerable). Some attackers used "rm", others used
"/bin/rm". A more recent example may be
The only thing you know for sure is the space after the "rm".
If you are sure to catch all possible combinations a pcre rule
should reduce the fps significantly (I'll try to write a rule
after a night of sleep; can't think straight right now).
More information about the Snort-sigs