Cisco Cisco Web Security Appliance S690 User Guide

The access log file records the URL category for each transaction in the scanning verdict information 
section of each entry. 

.

The Web Security appliance uses a regular expression syntax that differs slightly from the regular 
expression syntax used by other Velocity pattern-matching engine implementations. Further, the 
appliance does not support using a backward slash to escape a forward slash. If you need to use a forward 
slash in a regular expression, simply type the forward slash without a backward slash.

Technically, AsyncOS for Web uses the Flex regular expression analyzer. For more detailed information 
about how it reads regular expressions, see http://flex.sourceforge.net/manual/Patterns.html.

You can use regular expressions in the following locations:

Custom URL categories for Access Policies. When you create a custom URL category to use with 
Access Policy groups, you can use regular expressions to specify multiple web servers that match 
the pattern you enter.

Custom user agents to block. When you edit the applications to block for an Access Policy group, 
you can use regular expressions to enter specific user agents to block. 

Regular expressions that perform extensive character matching consume resources and can affect system 
performance. For this reason, regular expressions should be cautiously applied. 

Policy: Protocols and User Agents, page 9-13

Regular expressions are rules that typically use the word “matches” in the expressions. They can be 
applied to match specific URL destinations or web servers. For example, the following regular 
expression matches any pattern containing “

blocksite.com

”:

\.blocksite\.com

 

Consider the following regular expression example: 

server[0-9]\.example\.com

 

In this example, 

server[0-9]

 matches 

server0

, 

server1

, 

server2

, ..., 

server9

 in the domain 

example.com

.