ZyXEL Communications ZyWall ATP series User Manual page 546

The following table describes the fields in this screen.
Table 221 Configuration > Security Service > IDP > Custom Signatures > Add/Edit
LABEL
Name
Signature ID
Information
Severity
Platform
Classification Type
Frequency
Threshold
Header Options
Network Protocol
Type Of Service
Identification
Fragmentation
Fragment Offset
Time to Live
Chapter 30 IDP
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.
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.
Categorize the attack type 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 Fragment 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.
ZyWALL ATP Series User's Guide
546
Table 218 on page 540 as a reference.