Fortinet Network Device IPS - Manual (Page 31)

Custom signatures Creating custom signatures
FortiGate IPS User Guide Version 3.0 MR7
01-30007-0080-20080916
31
--tcp_flags
[!|*|+]
[,]; Specify the TCP flags to match in a packet.
•
S: Match the SYN flag.
• A: Match the ACK flag.
• F: Match the FIN flag.
• R: Match the RST flag.
• U: Match the URG flag.
• P: Match the PSH flag.
• 1: Match Reserved bit 1.
• 2: Match Reserved bit 2.
• 0: Match No TCP flags set.
• +: Match on the specified bits, plus any
others.
• *: Match if any of the specified bits are set.
• !: Match if the specified bits are not set.
The first part if the value () defines
the bits that must present for a successful match.
For example:
--tcp_flags AP
only matches the case where both A and P bits
are set.
The second part ([,]) is optional,
and defines the additional bits that can present
for a match. For example:
tcp_flags S,12
matches the following combinations of flags: S, S
and 1, S and 2, S and 1 and 2.
The modifiers !, * and + can not be used in the
second part.
--window_size
[!]; Check for the specified TCP window size.
You can specify the window size as a
hexadecimal or decimal integer. A hexadecimal
value must be preceded by 0x.
To have the FortiGate search for the absence of
the specified window size, add an exclamation
mark (!) before the window size.
Table 6: TCP header keywords (Continued)
Keyword and Value Description