ZyXEL Communications ZyXEL ZyWALL USG-1000, User Manual

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Chapter 31 IDP
ZyWALL USG 2000 User’s Guide
519
Snort Signatures
You may want to refer to open source Snort signatures when creating custom
ZyWALL ones. Most Snort rules are written in a single line. Snort rules are divided
into two logical sections, the rule header and the rule options as shown in the
following example:
alert tcp any any -> 192.168.1.0/24 111 (content:”|00 01 a5|”;
msg:”mountd access”;)
The text up to the first parenthesis is the rule header and the section enclosed in
parenthesis contains the rule options. The words before the colons in the rule
options section are the option keywords.
The rule header contains the rule's:
• Action
• Protocol
• Source and destination IP addresses and netmasks
• Source and destination ports information.
The rule option section contains alert messages and information on which parts of
the packet should be inspected to determine if the rule action should be taken.
These are some equivalent Snort terms in the ZyWALL.
Table 154 ZyWALL - Snort Equivalent Terms
ZYWALL TERM SNORT EQUIVALENT TERM
Type Of Service tos
Identification id
Fragmentation fragbits
Fragmentation Offset fragoffset
Time to Live ttl
IP Options ipopts
Same IP sameip
Transport Protocol
Transport Protocol: TCP
Port (In Snort rule header)
Flow flow
Flags flags
Sequence Number seq
Ack Number ack
Window Size window
Transport Protocol: UDP (In Snort rule header)