ZyXEL ZyWALL USG 2000 User Guide - Page 589
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Chapter 34 IDP Table 159 Configuration > Anti-X > IDP > Custom Signatures > Add/Edit (continued) LABEL DESCRIPTION Payload Size This field may be used to check for abnormally sized packets or for detecting buffer overflows. Select the check box, then select Equal, Smaller or Greater and then type the payload size. Add Edit Remove # Offset Content Caseinsensitive Decode as URI Stream rebuilt packets are not checked regardless of the size of the payload. Click this to create a new entry. Select an entry and click this to be able to modify it. Select an entry and click this to delete it. This is the entry's index number in the list. This field specifies where to start searching for a pattern within a packet. For example, an offset of 5 would start looking for the specified pattern after the first five bytes of the payload. Type the content that the signature should search for in the packet payload. Hexadecimal code entered between pipes is converted to ASCII. For example, you could represent the ampersand as either & or |26| (26 is the hexadecimal code for the ampersand). Select Yes if content casing does NOT matter. A Uniform Resource Identifier (URI) is a string of characters for identifying an abstract or physical resource (RFC 2396). A resource can be anything that has identity, for example, an electronic document, an image, a service ("today's weather report for Taiwan"), a collection of other resources. An identifier is an object that can act as a reference to something that has identity. Example URIs are: ftp://ftp.is.co.za/rfc/rfc1808.txt; ftp scheme for File Transfer Protocol services http://www.math.uio.no/faq/compression-faq/part1.html; http scheme for Hypertext Transfer Protocol services mailto:[email protected]; mailto scheme for electronic mail addresses telnet://melvyl.ucop.edu/; telnet scheme for interactive services via the TELNET Protocol Select Yes for the signature to search for normalized URI fields. This means that if you are writing signatures that includes normalized content, such as %2 for directory traversals, these signatures will not be triggered because the content is normalized out of the URI buffer. For example, the URI: /scripts/..%c0%af../winnt/system32/cmd.exe?/c+ver will get normalized into: /winnt/system32/cmd.exe?/c+ver ZyWALL USG 2000 User's Guide 589
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