Cisco Systems ASA 5585-X Manual De Usuario

FTP command filtering and security checks are provided using strict FTP inspection for improved 
security and control. Protocol conformance includes packet length checks, delimiters and packet format 
checks, command terminator checks, and command validation. 

Blocking FTP based on user values is also supported so that it is possible for FTP sites to post files for 
download, but restrict access to certain users. You can block FTP connections based on file type, server 
name, and other attributes. System message logs are generated if an FTP connection is denied after 
inspection.

If you want FTP inspection to allow FTP servers to reveal their system type to FTP clients, and limit the 
allowed FTP commands, then create and configure an FTP map. You can then apply the FTP map when 
you enable FTP inspection.

To create an FTP map, perform the following steps:

(Optional) Add one or more regular expressions for use in traffic matching commands according to the 
general operations configuration guide. See the types of text you can match in the match commands 
described in 

(Optional) Create one or more regular expression class maps to group regular expressions according to 
the general operations configuration guide.

(Optional) Create an FTP inspection class map by performing the following steps.

A class map groups multiple traffic matches. Traffic must match all of the match commands to match 
the class map. You can alternatively identify match commands directly in the policy map. The difference 
between creating a class map and defining the traffic match directly in the inspection policy map is that 
the class map lets you create more complex match criteria, and you can reuse class maps.

To specify traffic that should not match the class map, use the match not command. For example, if the 
match not command specifies the string “example.com,” then any traffic that includes “example.com” 
does not match the class map.

For the traffic that you identify in this class map, you can specify actions such as drop, drop-connection, 
reset, mask, set the rate limit, and/or log the connection in the inspection policy map.

If you want to perform different actions for each match command, you should identify the traffic directly 
in the policy map.

Create the class map by entering the following command:

ciscoasa(config)# class-map type inspect ftp [match-all | match-any] class_map_name

ciscoasa(config-cmap)# 

Where class_map_name is the name of the class map. The match-all keyword is the default, and 
specifies that traffic must match all criteria to match the class map. The match-any keyword 
specifies that the traffic matches the class map if it matches at least one of the criteria. The CLI 
enters class-map configuration mode, where you can enter one or more match commands.

(Optional) To add a description to the class map, enter the following command:

ciscoasa(config-cmap)# description string

(Optional) To match a filename for FTP transfer, enter the following command:

ciscoasa(config-cmap)# match [not] filename regex [regex_name | 

regex_class_name]

Where the regex_name is the regular expression you created in 

. The class regex_class_name 

is the regular expression class map you created in 

.