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Next: Installing Snort Inline Up: Inline Mode Previous: New STREAM4 Options for   Contents


Replacing Packets with Snort Inline

Additionally, Jed Haile's content replace code allows you to modify packets before they leave the network. For example: 

alert tcp any any <> any 80 (msg: "tcp replace"; content:"GET"; replace:"BET";)
alert udp any any <> any 53 (msg: "udp replace"; \
    content: "yahoo"; replace: "xxxxx";)

These rules will comb TCP port 80 traffic looking for GET, and UDP port 53 traffic looking for yahoo. Once they are found, they are replaced with BET and xxxxx, respectively. The only catch is that the replace must be the same length as the content.


Steven Sturges 2007-05-11
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