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Flooded failed login attempts

Posted on 2016-08-22
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Last Modified: 2016-09-20
Hi Experts,

I'm having an issue with my SBS 2008 server is flooded with failed login attempts like the below example. It doesnt tell me where its coming from or how to stop it - any ideas on how do identify the source and block it.

We currently have  a smoothwall setup as our firewall, which i am trying to get changed for a UTM.

Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-a5ba-3e3b0328c30d}" />
    <EventID>4625</EventID>
    <Version>0</Version>
    <Level>0</Level>
    <Task>12544</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8010000000000000</Keywords>
    <TimeCreated SystemTime="2016-08-23T00:45:43.802Z" />
    <EventRecordID>260608564</EventRecordID>
    <Correlation />
    <Execution ProcessID="876" ThreadID="972" />
    <Channel>Security</Channel>
    <Computer>SBS-SERVER.domain.local</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="SubjectUserSid">S-1-0-0</Data>
    <Data Name="SubjectUserName">-</Data>
    <Data Name="SubjectDomainName">-</Data>
    <Data Name="SubjectLogonId">0x0</Data>
    <Data Name="TargetUserSid">S-1-0-0</Data>
    <Data Name="TargetUserName">ADMINISTRATOR</Data>
    <Data Name="TargetDomainName">
    </Data>
    <Data Name="Status">0xc000006d</Data>
    <Data Name="FailureReason">%%2313</Data>
    <Data Name="SubStatus">0xc000006a</Data>
    <Data Name="LogonType">3</Data>
    <Data Name="LogonProcessName">NtLmSsp </Data>
    <Data Name="AuthenticationPackageName">NTLM</Data>
    <Data Name="WorkstationName">
    </Data>
    <Data Name="TransmittedServices">-</Data>
    <Data Name="LmPackageName">-</Data>
    <Data Name="KeyLength">0</Data>
    <Data Name="ProcessId">0x0</Data>
    <Data Name="ProcessName">-</Data>
    <Data Name="IpAddress">-</Data>
    <Data Name="IpPort">-</Data>
  </EventData>
</Event>
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Question by:isdd2000
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8 Comments
 
LVL 32

Assisted Solution

by:Dr. Klahn
Dr. Klahn earned 500 total points (awarded by participants)
ID: 41766230
Quick and dirty:  Install Microsoft TCP View on the afflicted system and watch the IP addresses to see which one(s) is flooding the server.

Slower but provably correct:  Install Microsoft Process Monitor, restrict the events to TCP Connects and Login, and run it for a while.  Then read out the log, correlate connects and login attempts, and see which IP address(es) is flooding the server.
0
 

Author Comment

by:isdd2000
ID: 41766281
TCP View is a little difficult to go through everything given its a domain controller the list just keeps updating & i cannot see anything even when paused.

Ill try Microsoft Process Monitor now, i have Trend running a local firewall for Intrusion prevention but it still occurring.
0
 
LVL 37

Expert Comment

by:Kimputer
ID: 41766572
Probably it's internal traffic only (and your firewall probably blocks external traffic).
Probably the fastest way to weed it out, is to ask employees to stop using their computers (and close all open windows and apps) for a while. The traffic will now be more manageable.
It could be malware trying brute force, but could also be something as innocent as a misconfigured printer/storage device that tries to deliver files to the server (but doesn't have the correct credentials input).
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LVL 30

Assisted Solution

by:pgm554
pgm554 earned 500 total points (awarded by participants)
ID: 41767358
Do you have Remote Web Access set up?
If so ,it's just folks trying to break into your server by using bots.
Unless you take it off the net,there's little you can do.
0
 

Author Comment

by:isdd2000
ID: 41779323
Hi Kimputer,

If its local traffic wouldnt the event log have a local ip that is the cause?

pgm554,

We do have RWW setup and i took IIS offline and the attack still came in.
0
 

Author Comment

by:isdd2000
ID: 41779327
Also they have tried close to 400 different usernames it can not be an internal device misconfigured.
0
 
LVL 37

Accepted Solution

by:
Kimputer earned 1000 total points (awarded by participants)
ID: 41779679
Then it sounds like malware. Install Wireshark on the RDP server. Then start a capture on the NIC with
port 3389
(or which ever port it should be).
Obviously, ask the people to stop working for a bit. If not attack pattern is visible (please note your own IP will show up as a stream if you use RDP to connect to the server), then try again with:
port 80 or port 445 or port 135 or port 137  or port 139
Check for attach patterns again.
If still nothing, then try again without any filter (or if you use RDP, use
not port 3389
)
0
 
LVL 32

Expert Comment

by:Dr. Klahn
ID: 41806176
System requested close
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