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How to block W32.Blaster in an enterprise MAN/WAN at Cisco Routers

Posted on 2004-05-01
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Last Modified: 2010-04-17
I have a customer with 9 locations connected together via T1 circuts.  The routers at the sites are Cisco 1721's with T1 WICs.   There are 60 Win2K servers with an Active Directory DC at each site.  Cisco's recommendation only addresses the router at the edge and will not work for the other routers in this scenerio.   Is there any way to block Blaster at the router level, using the 1721's that are currently in place, without stopping valid communications between sites and servers?
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Question by:JCRussell
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by:lrmoore
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Simply block icmp echo on the local lan interface:

access-list 102 deny icmp any any echo
access-list 102 permit ip any any

Interface FastEthernet 0
 access-group 102 in


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by:JCRussell
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From the activity that we are seeing, it appears that Blast is scanning ports.  All of the machines that have Blast are sending epmap packets with consecutive port numbers.  At least all the machines that are scanning have Blast.  Is this Blast or something else?  Will blocking icmp echos stop this activity?
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by:lrmoore
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blocking icmp echo requests will localize the outbreak to the local lan. The blast of icmp is what kills networks. At the very least, this will keep the infection localized and keep the extra traffic off of your WAN links until you can eradicate it.
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by:mikebernhardt
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Also block TCP port 135 (DCom), which is what Blaster propagates itself with once it finds a live host. Although it will try port 80 also...
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by:JCRussell
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Won't blocking 135 stop file sharing, etc.?
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mikebernhardt earned 125 total points
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Nope. It's not used for anything useful. It amost seems as if it was designed to give hackers a good tool for worms.

http://grc.com/dcom/
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After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

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