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| Subject: | RE: Blocking IM |
|---|---|
| Date: | Wed, 7 Dec 2005 11:37:02 -0700 |
An alternative solution to using expensive IDS or Web Filtering products is BLACKHOLE DNS. Easy to setup and free if you have your own DNS server. Here is some information for configuring blackhole DNS. It was originally used to prevent malware, but it can be easily used to block instant messengers as well. The idea is that your DNS server resolves the DNS name used for the login process. You point the DNS alias to an internal IP address on your network. If users can't login, they won't be using instant messengers. It has worked for us. http://www.bleedingsnort.com/blackhole-dns/ http://www.bleedingsnort.com/article.php?story=20050620215129947&query=blackhole Here are the DNS names we use for blocking instant messengers: AOL login.oscar.aol.com screenname.aol.com aimexpress.aol.com aim.aol.com Yahoo msg.yahoo.com messenger.yahoo.com MSN messenger.hotmail.com msgr.hotmail.com webmessenger.msn.com GOOGLE talk.google.com ** *From:* Morales, David (Seta) [mailto:David_Morales@onr.navy.mil] *Sent:* Tuesday, December 06, 2005 12:51 PM *To:* firewalls@securityfocus.com *Cc:* Amiryar, Edris (Seta) *Subject:* Blocking IM We are blocking IM at the Firewall (juniper 5200) and through Surf-control (Web Filtering product, but we are still able to connect to Yahoo IM. Has anyone been able to do this successfully? And, does anyone have a list of ports to block so we cannot get to this IM? Thanks in advance, David Morales moraled@onr.navy.mil
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