Could it be some sort of Scheduled Task causing this? (Late to the party)
Sent from my (new!) BlackBerry, which may make me an antiques dealer, but it's reliable as hell for email delivery :-) -----Original Message----- From: Melvin Backus <[email protected]> Sender: [email protected]: Thu, 24 Apr 2014 16:34:33 To: [email protected]<[email protected]> Reply-to: [email protected] Subject: RE: [NTSysADM] RE: DNS server settings getting changed OK, regmon says it's svchost, so now I've just got to track down which service that instance is handling, and hope it isn't more than one. :) -- There are 10 kinds of people in the world... those who understand binary and those who don't. From: [email protected] [mailto:[email protected]] On Behalf Of Andrew S. Baker Sent: Thursday, April 24, 2014 12:24 PM To: ntsysadm Subject: Re: [NTSysADM] RE: DNS server settings getting changed You're now left with wireshark and/or Process Monitor for troubleshooting. ASB http://XeeMe.com/AndrewBaker<http://xeeme.com/AndrewBaker> Providing Virtual CIO Services (IT Operations & Information Security) for the SMB market... On Thu, Apr 24, 2014 at 11:19 AM, Melvin Backus <[email protected]<mailto:[email protected]>> wrote: I was actually already doing that, just in case. No joy. Supported by the fact that gpupdate /force doesn't induce the problem. -- There are 10 kinds of people in the world... those who understand binary and those who don't. From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Charles F Sullivan Sent: Thursday, April 24, 2014 11:12 AM To: [email protected]<mailto:[email protected]> Subject: Re: [NTSysADM] RE: DNS server settings getting changed I would at least run rsop.msc on one of the affected machines to make sure, as this still sounds to me like a possibility. On Thu, Apr 24, 2014 at 10:32 AM, Andrew S. Baker <[email protected]<mailto:[email protected]>> wrote: The other place to check, since you pointed out that it's pointing to your own DNS server, is Group Policy. Those servers may be in a group or OU affected by an explicit push of DNS server info. Regards, ASB http://XeeMe.com/AndrewBaker<http://xeeme.com/AndrewBaker> Providing Virtual CIO Services (IT Operations & Information Security) for the SMB market... On Thu, Apr 24, 2014 at 9:41 AM, Melvin Backus <[email protected]<mailto:[email protected]>> wrote: No reason I can think of. Even if they resolved, they wouldn't be accessible. While I did consider malware, the fact that it reverts to our internal servers, and that those were where things would have legitimately pointed 6 weeks ago, make me think it's more likely something else, but we've run out of ideas on what at this point, hence my query to the list. I try to never rule anything out until I can prove it's something else. It just gets moved down the list. -- There are 10 kinds of people in the world... those who understand binary and those who don't. From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Micheal Espinola Jr Sent: Thursday, April 24, 2014 9:25 AM To: ntsysadm Subject: Re: [NTSysADM] RE: DNS server settings getting changed That software would be per-client. Its a DNS hijacking trojan. It seems odd that these systems are getting your Domain DNS. Would those servers be providing resolution to systems that would otherwise not? Would someone want to use your Domain DNS over what you are configuring? -- Espi On Thu, Apr 24, 2014 at 6:15 AM, Melvin Backus <[email protected]<mailto:[email protected]>> wrote: No, it's changing back to our domain DNS. Just curious though, did that only affect the machine with the software or was it able to touch other machines across the network? -- There are 10 kinds of people in the world... those who understand binary and those who don't. From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Jimmy Tran Sent: Thursday, April 24, 2014 9:12 AM To: [email protected]<mailto:[email protected]> Subject: [NTSysADM] RE: DNS server settings getting changed Had this problem happen to two different clients. The machines someone got some software called DNSchanger installed. It would change DNS to 8.8.8.8 and 8.8.4.4. Are those the IP's its changing to? From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Melvin Backus Sent: Thursday, April 24, 2014 5:27 AM To: [email protected]<mailto:[email protected]> Subject: [NTSysADM] DNS server settings getting changed OK, this has been driving us nuts for a couple of days now. One of our remote sites is seeing seemingly random PCs change their DNS server settings. They're all configured to get them from the DHCP server, and it has the correct DNS servers. All the PCs do in fact get the correct settings when they get or renew an IP. That all seems to be working as we expect. But periodically we'll see a machine change the DNS servers to something else. This causes applications to start failing because the hosts they need no longer resolve. As soon as the PC renews it's IP, whether automatically or manually, everything goes back to normal and stuff works again. We have a short term fix (force the DNS server settings manually instead of DHCP) but that doesn't explain what's going on, and since we're using this same setup in 20 offices it also begs the question of why just this office. Background: Multiple small offices with either /28 or /27 networks. They are publicly routable IPs due to requirements for a partner VPN. The DHCP server is on the Juniper SSG FW. It servers two pools, one for PCs, another for phones. The PC subnet is publicly routable, the phone subnet is a non-routable 10.x subnet with matching ranges. (12.x.x.x/27 and 10.x.x.x/27). All DNS points to the home office. Until recently these pointed strictly to our domain DNS servers. As part of the VPN requirement we have set up a second set of DNS servers which are used to resolve hosts in the partner's domains. This is done with conditional forwarders. Partner DNS traffic gets resolved by their servers, everything else goes to our domain DNS or the Internet as required. This all works fine except in a single office. Even in that office it worked fine for weeks and has suddenly started this "revert" behavior. When the PCs change, they go back to pointing to our domain DNS which can't resolve the partner hosts. My question becomes (sorry it took so long) how do we track what is actually changing the DNS settings? I can tell when it happens fairly easily, but nothing in the event logs, etc., seems to indicate what triggered it, or what process is doing it. It doesn't happen as part of a DHCP operation as best we can tell. -------------------- Melvin Backus | Sr. Systems Analyst | Byers Engineering Company | 404.497.1565<tel:404.497.1565> Service Desk | 404-497-1599<tel:404-497-1599> | http://servicedesk.byers.com -- There are 10 kinds of people in the world... those who understand binary and those who don't. -- Charlie Sullivan Sr. Windows Systems Administrator Boston College 197 Foster St. Room 367 Brighton, MA 02135 617-552-4318<tel:617-552-4318>
