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The following table describes the fields in this screen.
Table 137 Anti-X > IDP > Custom Signatures > Add/Edit
LABEL
Name
Signature ID
Information
Severity
Platform
Service
Policy Type
Frequency
Threshold
Header Options
Network Protocol
Type Of
Service
Identification
Fragmentation
Fragmentation
Offset
Time to Live
ZyWALL USG 1000 User's Guide
DESCRIPTION
Type the name of your custom signature. You may use 1-31 alphanumeric
_
characters, underscores(
), or dashes (-), but the first character cannot be a
number. This value is case-sensitive.
Duplicate names can exist but it is advisable to use unique signature names that
give some hint as to intent of the signature and the type of attack it is supposed to
prevent. Refer to (but do not copy) the packet inspection signature names for
hints on creating a naming convention.
A signature ID is automatically created when you click the Add icon to create a
new signature. You can edit the ID to create a new one (in the 9000000 to
9999999 range), but you cannot use one that already exists. You may want to do
that if you want to order custom signatures by SID.
Use the following fields to set general information about the signature as denoted
below.
The severity level denotes how serious the intrusion is. Categorize the
seriousness of the intrusion here. See
Some intrusions target specific operating systems only. Select the operating
systems that the intrusion targets, that is, the operating systems you want to
protect from this intrusion. SGI refers to Silicon Graphics Incorporated, who
manufactures multi-user Unix workstations that run the IRIX operating system
(SGI's version of UNIX). A router is an example of a network device.
Select the IDP service group that the intrusion exploits or targets. See
on page 428
for a list of IDP service groups. The custom signature then appears
in that group in the IDP > Profile > Group View screen.
Categorize the type of intrusion here. See
Recurring packets of the same type may indicate an attack. Use the following field
to indicate how many packets per how many seconds constitute an intrusion
Select Threshold and then type how many packets (that meet the criteria in this
signature) per how many seconds constitute an intrusion.
Configure signatures for IP version 4.
Type of service in an IP header is used to specify levels of speed and/or reliability.
Some intrusions use an invalid Type Of Service number. Select the check box,
then select Equal or Not-Equal and then type in a number.
The identification field in a datagram uniquely identifies the datagram. If a
datagram is fragmented, it contains a value that identifies the datagram to which
the fragment belongs. Some intrusions use an invalid Identification number.
Select the check box and then type in the invalid number that the intrusion uses.
A fragmentation flag identifies whether the IP datagram should be fragmented,
not fragmented or is a reserved bit. Some intrusions can be identified by this flag.
Select the check box and then select the flag that the intrusion uses.
When an IP datagram is fragmented, it is reassembled at the final destination.
The fragmentation offset identifies where the fragment belongs in a set of
fragments. Some intrusions use an invalid Fragmentation Offset number. Select
the check box, select Equal, Smaller or Greater and then type in a number
Time to Live is a counter that decrements every time it passes through a router.
When it reaches zero, the datagram is discarded. Usually it's used to set an upper
limit on the number of routers a datagram can pass through. Some intrusions can
be identified by the number in this field. Select the check box, select Equal,
Smaller or Greater and then type in a number.
Chapter 29 IDP
Table 131 on page 426
as a reference.
Table 132 on page 427
as a reference.
Table 133
437
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