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Code Issues Releases Wiki Activity

portscan: update manpage about --grscan caveats

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This commit is contained in:
Jan Engelhardt
2009-01-10 05:23:43 +01:00
parent 598c7ede37
commit 31c01cf107
1 changed files with 5 additions and 1 deletions
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6
extensions/libxt_portscan.man
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@@ -20,7 +20,11 @@ connection was torn down after completion of the 3-way handshake.
\fB--grscan\fR
Match if data in the connection only flew in the direction of the remote side,
e.g. if the connection was terminated after a locally running daemon sent its
identification. (e.g. openssh)
identification. (E.g. openssh, smtp, ftpd.) This may falsely trigger on
warranted single-direction data flows, usually bulk data transfers such as
FTP DATA connections or IRC DCC. Grab Scan Detection should only be used on
ports where a protocol runs that is guaranteed to do a bidirectional exchange
of bytes.
.PP
NOTE: Some clients (Windows XP for example) may do what looks like a SYN scan,
so be advised to carefully use xt_portscan in conjunction with blocking rules,