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how can I tell if my SBS 2003 and network have been owned by a hacker?

I looked at my security logs this morning and found many suspicious events within the last 24 hours, including:

- my logon used while I was asleep
- there are more than 600 ANONYMOUS LOGON domain NT AUTHORITY events
- there are more than 300 logons from one of the machines on my network

I suspect my network has been hacked. Can some kind expert please help with these questions:
- are there any legitimate reasons why some process might logon on my behalf?
- why do machines logon? is there any possible legitimate reason a machine would logon so many times?
- are there other things I should investigate to confirm a network intrusion / compromise?
- is there a checklist somewhere of how to recover a compromised network?

Thanks.
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bfitler
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bfitler
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Jeffrey Kane - TechSoEasyPrincipal ConsultantCommented:
Although you did not provide the Event ID's for these, which would help to explain them a bit better, I can give you a basic overview:

There are legitimate reasons why a process would logon under your account... if you used your account in the configuration of a particular program or service.  Often, people wrongly configure SQL server with their user account as the owner, or for the maintenance plan.  There might be a scheduled task that was created with your credentials.  Filter the security event log for ONLY these logons and see if there is a pattern, such as it being the same time every night, or once a week at the same time, etc.

Machines log on any time that machine needs to access any resource on the server.  I would be suspicious of a machine that has 300 logons in a 24-hour period only if it is significantly more than you have on any other machine, and only if there are a number of logons after-hours.  However, if a user does not log out of their computer, that machine would continue to check with the server every 15 minutes or so just to update it's Kerberos Security setting.  So, check to make sure that the user is logging out properly, and take a quick look to make sure that there isn't anything installed on the computer that shouldn't be there.

Anonymous Logons are quite common, are these Event 684 for Account Management?  Because 6very 60 minutes on a domain controller a background thread searches all members of administrative groups (such as domain, enterprise, and schema administrators) and applies a fixed security descriptor on them.  If you had 3 or 4 members of any of these groups, you would easily see hundreds of events.   If you're seeing a rash of Event 538/540 Logon/Logoff then is there a specific machine name listed?  Because any machine that you have connected to your network which is not part of the domain will generate this event.

Things to investigate?
You can always check for a rootkit, which is a hacker program that runs below the radar (outside of the Windows OS) which is often used to take advantage of your storage space by creating a rogue FTP server.  Check for that with this: http://www.sysinternals.com/Utilities/RootkitRevealer.html

For a complete overview of what you need to know and do about securing your SBS Network, please see http://sbsurl.com/secnet

Jeff
TechSoEasy
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bfitlerAuthor Commented:
Great answer, Jeff - you've set my mind about 80% at ease. Some follow-ups:

- I looked closer at the times when my login was used. During one period, 19 events were recorded within 30 seconds (event IDs 538, 540, 576) on intervals ranging from 1h33m to 1h58m. I noticed a smaller number of correlated events in the security log on another computer. How can I track down the responsible application?

- Many of the ANONYMOUS logons are from machines on the network not joined to the domain, as you predicted. One of the computers in the domain, however, also generates ANONYMOUS logons (Event ID 540, Logon Type:3, Logon Process: NtLmSsp, Authentication Package: NTLM). How can I validate such events?

\bill
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bfitlerAuthor Commented:
Let me clarify first follow-up: the responsible process (identified in events 540) is Kerberos - but I can't tell whether I'm logging into the computer (presumably causing Kerberos to login as a result), or Kerberos is logging in for some other reason.
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Jeffrey Kane - TechSoEasyPrincipal ConsultantCommented:
Kerberos is not something that would log in, it's a security protocol (http://en.wikipedia.org/wiki/Kerberos_(protocol)).

If you are getting Kerberos Type 3 errors, then that workstation either is not synchronizing it's clock with the server correctly (since Kerberos is based on a ticket system which requires time synchronization), or there is software installed on that workstation that's causing it.  So, I'd check the time sync first.

How to configure an authoritative time service in Windows 2003: http://support.microsoft.com/kb/816042
How to synchronize the time with the Windows Time service in Windows XP:  http://support.microsoft.com/kb/307897

Then if that doesn't do the trick, compare what is installed on that workstation with one that isn't causing the errors... that's about the easiest way to find the culprit.

As for finding the source for your logins, you might want to use something like this:
http://manageengine.adventnet.com/products/opmanager/download.html

The free version allows monitoring and management of up to 20 devices, usually enough for an SBS network.  I like their products since they work, and they are generally free for SBS-sized environments.

Jeff
TechSoEasy
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