The vulnerability is based on a sequence of some number of special packets targeted *at* the router's interface (i.e., not packets that are going to be routed *through*). The packets do not use the normal IP protocols such as TCP/UDP/ICMP, but something different. So, first thing is that if you're only allowing TCP, UDP, ICMP, and maybe IPSEC then you may be ok. Even so, you should also as part of your ACLs be dropping packets targeted directly AT your router's interface address unless you know what they do and where they are from. On Thu, 2003-07-17 at 10:14, Gustavo Kruel wrote: > Hi all. > > I saw today the vulnerability alert on Cisco IOS. The workaround is to > implement ACL?s that block packets from unknown sources directed to an > exposed interface. > > Thinking about a perimeter router, i have one router with a "tcp any any > established" ACL. I also have ICMP opened in this same router, any -> any. > Are this lines enough to make this interface vulnerable to the possible > attack? > > What do you think about it? > > > ---------------------------------------------------------------------------- > Attend the Black Hat Briefings & Training, July 28 - 31 in Las Vegas, the > world's premier technical IT security event! 10 tracks, 15 training sessions, > 1,800 delegates from 30 nations including all of the top experts, from CSO's to > "underground" security specialists. See for yourself what the buzz is about! > Early-bird registration ends July 3. This event will sell out. www.blackhat.com > ---------------------------------------------------------------------------- -- James V. Fields ---------------------------------------------------------------------------- Attend the Black Hat Briefings & Training, July 28 - 31 in Las Vegas, the world's premier technical IT security event! 10 tracks, 15 training sessions, 1,800 delegates from 30 nations including all of the top experts, from CSO's to "underground" security specialists. See for yourself what the buzz is about! Early-bird registration ends July 3. This event will sell out. www.blackhat.com ----------------------------------------------------------------------------
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