Security Basics mailing list archives
RE: Spyware blocking with HOSTS file on DNS server
From: "Dan Lynch" <dan.lynch () placer ca gov>
Date: Tue, 01 Feb 2005 10:18:29 -0800
Thanks for the input Andrew and Joey, but I think you might misunderstand my goals here. The HOSTS files are precompiled and maintained. I don't plan on doing it myself. See for example: http://www.mvps.org/winhelp2002/hosts.htm http://www.dozleng.com/hpguru/ http://www.everythingisnt.com/hosts.html http://www.ecst.csuchico.edu/%7Eatman/spam/adblock.shtml http://www.accs-net.com/hosts/get_hosts.html But with the wealth of maintained lists available, which ones have clear policies for inclusion and removal? That is, how *well* maintained are they? Opinions anyone? Sure enough, our McAfee e500 WebShield proxy server doesn't allow access to the HOSTS file, so the conversion to zone format for import to our DNS server would be required. I'd need do nothing but convert to a zone file and import to my DNS server. See for example: http://pgl.yoyo.org/adservers/index.php http://www.geocities.com/yosponge/updates.html But my DNS skills are limited, and the specifics of this usage are over my head. What gotchas exist? Anyone tried it? The point is I *don't* want to manage this all myself. I want a prefab solution. And of the available choices, I don't wanna pay for nothin'! Particularly considering (1) the vast expense of vendor provided solutions (five-figures up front, then yearly subscription, plus hardware, OS, and administration overhead of it all); and (2) that the vast bulk of our spyware problem goes away if browsers can't access the sites that generate it. The cost/benefit ratio of vendor solutions doesn't justify the acquisition in my mind. To me, an improved process has an inherent advantage over an acquired product. Another lister mentioned a report that someone "toasted her proxy server by using 127.0.0.1". What happens at the IP layer when the proxy attempts dozens (or hundreds) of connections to a non-existent listener on the loopback? What if a listener *does* exist? For example, in our environment, browsers are configured to connect to the proxy on port 1500. The proxy the initiates the outbound connection to the destination web server, generally on port 80. If the web server name resolves to loopback, we have the proxy attempting to connect to itself on port 80. Do we wait for TCP timeout? What if our proxy *were* listening on port 80? Would a 404 NOT FOUND result? Would the behavior be different if DNS instead resolved the end point to 0.0.0.0? Again, thanks everyone for any input here. Dan Lynch, CISSP County of Placer Auburn, CA
"Andrew Shore" <andrew.shore () holistecs com> 2/1/2005 1:33:00 AM
I have to agree, staying on top of a tack like this is a huge commitment and one you'll probably never achieve. There are more and more of these site springing up every day. I would recommend Websense with the spyware module. Just my 2 cents but I think you're barking up the wrong tree. Andy -----Original Message----- From: Johnson, Joey [mailto:Joey.Johnson () MWAA com] Sent: 28 January 2005 20:39 To: Dan Lynch; security-basics () securityfocus com Subject: RE: Spyware blocking with HOSTS file on DNS server Any particular reason you don't want to manage all this yourself manually? There are several good enterprise level solutions out there. Some of them free. You mentioned you're in a Windows domain so have a browse at this site and go from there? http://www.winnetmag.net/WindowsSecurity/Article/ArticleID/44624/44624.h tml -----Original Message----- From: Dan Lynch [mailto:dan.lynch () placer ca gov] Sent: Friday, January 28, 2005 1:45 PM To: security-basics () securityfocus com Subject: Spyware blocking with HOSTS file on DNS server Greetings list, Recent plagues of spyware/adware on our ~2000-client network has us interested in strategies for eliminating it. One path we're investigating is the use of compiled lists of known spyware/adware host names in HOSTS file format that resolve them to loopback. But since all our clients proxy web traffic through a central point, no name resolution is ever done at the client and a HOSTS file would do us no good at the desktop. Instead our proxy server performs all name resolution against an internal DNS server. Also, we'd like to centrally manage the solution. Questions follow: - list policies and practices We'd like to find a compiled HOSTS file with clear policies and transparent practices for inclusion and removal. Of the dozen or so HOSTS files I've found, none seem to meet that desire. Anyone have experience with a source that might be, um... "enterprise friendly"? Fairly regular updates would be good too, but it seems easy to find lists that are well maintained. - Loopback vs 0.0.0.0; connection use It seems some HOSTS lists like to resolve names to loopback (127.0.0.1), but others advocate resolving to 0.0.0.0. Which is better? If resolving to loopback, do we have to wait for the connection to timeout? But when resolving to 0.0.0.0, is the failure more immediate? Since this would all be taking place at a fairly busy proxy server, what would the impact of one or the other be to my connection pool? - HOSTS to zone conversion Since our proxy is a closed-source appliance we may be unable to put a HOSTS file on it. Further, if we can't make our DNS server pay attention to its own HOSTS file I assume that we'd need to convert any list to a zone file for import to the DNS server. New to me...any hints or tips here? Should I make an effort to eliminate all the host names and just pretend to be master of each adware domain? This is an oddball enough situation that my introductory DNS skills can't figure out the best way to do it. Any help would be appreciated. Any other gotchas or hints from the list are welcomed. I also welcome reference to lists or forums more closely focused on this area of interest. Thanks, Dan Lynch, CISSP County of Placer Auburn, CA
Current thread:
- RE: Spyware blocking with HOSTS file on DNS server Johnson, Joey (Jan 31)
- <Possible follow-ups>
- Re: Spyware blocking with HOSTS file on DNS server David Glosser (Feb 01)
- RE: Spyware blocking with HOSTS file on DNS server Andrew Shore (Feb 01)
- RE: Spyware blocking with HOSTS file on DNS server Dan Lynch (Feb 02)
- RE: Spyware blocking with HOSTS file on DNS server Barrie Dempster (Feb 03)
- Re: Spyware blocking with HOSTS file on DNS server David Glosser (Feb 02)