ZeroAccess network traffic analysis Reloaded

It's been 6 months since the last time I really sat down and looked into the network mysteries of ZeroAccess, described in my post ZeroAccess analysis part I - Network traffic.

I have seen several reports of changes to the binaries. Like this one from @MalwareMustDie and @hFireFOX

@MalwareMustDie Sirefef updated. No more MSCF usage, instead aplib compression, different startup method masquerading as google update.
— FireF0X (@hFireF0X) July 30, 2013

and also a couple of reports regarding the initial connect IP addresses (Commented on my blog and also by @unixfreaxjp

In the mean time the now infamous ZeroaAccess botnet have got lots of press coverage, especially for its bitcoin mining functionality, and seem to be as big if not bigger than ever. Reports vary in number, as always, but a fair guess is probably close to 10 million bots these days. The ZA botnet comes in two variants. One for bitcoin mining and one for click fraud.
So lets see if the betwork traffic from these bots have changed much or not:

1. The bot wants to know where in the world it's installed

This is done by a geoIP lookup towards the maxmind geoIP database. DNS lookup and HTTP query for lookup expected.

 Thats excactly the first thing that happens.  The geoIP lookup contains country code, city, metro code and so on, but I guess that only country code is used.

2. Install and report

The bot is then expected to install itself and report back. Last time it reported back to 194.165.17.3 this time it has switched to 194.165.17.4.

The udp payload is port 53, but not DNS. Lets have a closer look: 

080e745d8e9c9e9853765c3529717a624e1d7ced

Looks like ZA have done little to further obfuscate the install traffic, but lets xor it it with the key, which is "LONG" and bit rotate for every iteration:

4f403b110L0000004e4f610413030000aL938f98

Byte 0-3: should be bot id

Byte 8-9: country code - in this case NO 

Byte 10: 61 OS version

The early conclusion was correct. Still reporting the same info at install time using the same XOR key and scheme.

3. Flashplayer install

For some reason the bot goes on to update the flashplayer

This is where the update ends on my virtual system. Not perfect...

4. Start to find alive supernodes

The bot want to get fully operational and starts looking for live Supernodes. The initial IP's are probably hardcoded. Some of them are actually the same as six mionths earlier. UDP to port 16464 is still the method used by the bot. The first hit on a supernode on udp port 16464 automatically shifts the communication to TCP on the same port. 

This should be requests to get P2P lists. Lets look inside:

UDP payload: 463fdb8b28948dabc9c0d199f08c0f06

We recognize this from earlier analysis as byte 4-7  (28948dab) wil be Lteg when XORed with the correct key(ftp2) and bitwise rotated left. No change here either.

The TCP traffic is the same as well. Update plugins:

cb:00:00:80:09:b5:28:3f:00:5c:00:00 -> get file 800000cb

01:00:00:00:3b:cd:03:3f:90:03:00:00 -> get file 00000001

00:00:00:80:9e:e2:0c:3f:00:2e:00:00 -> get file 80000000

The requests have not changed at all!

The answer is encrypted plugins.

5. Continue the search for P2P lists

The getL command should be answered with a retL command:

Payload:

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

Decrypted payload:

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

As before:

0e 02 fe ff -> 14.2.254.255 and so on...

No changes to the P2P communication either.

6. Final callback to tell the world it's alive

To register it self and letting the bot herder know the bor is ready it fakes ntp traffic

7. Conclusion

Even if the ZA binary and the obfuscation/camuflague of the malware binary and downloads do keep on changing it seems like the communication and the botnet main features stay the same.

No changes has really occured in the past 6 months. This is good for us, the good guys, trying to protect networks and clients as it is an easy task to detect ZA activity on a network. The installation, P2P traffic and call home traffic are all covered in my previous posts on ZA. 

ZeroAccess network detection 

This means we can move on to new analysis again and just relax and know that we do catch ZA on our networks.

Thanks to @MalwareMustDie for providing the sample for research.

Happy relaxing :)

Post publish refernces:
Symantect  - ZeroAccess Modifies Peer-to-Peer Protocol for Resiliency

ZeroAccess Network detection

If you are into NIDS you probably want to look into detecting ZeroAccess traffic on your network. It is still spreading and infecting computers through exploit kits. F-Secure said it was the most profitable and fastest growing botnet of 2012. In addition, not all NIDS vendors have signatures to detect this by default configuration.

For analysis of the network traffic look at my post «ZeroAccess analysis part I – Network traffic». I have also made a python script to check if a remote host is infected – infomation about that can be found in the post «Checking ZeroAccess with Python and Scapy»

ZeroAccess is not the worst thing to get on your network, but you never know when that is going to change or what other bad stuff is on your vulnerable hosts. And, of course, we do not want these guys to earn money on our watch.

1. Detect the installation

Detecting the installation phase of the bot is nice as we can then also look into the infection mechanism and aslo see what the host was vulnerable to and fix it.

During the installation the bot talks to a set of hardcoded addresses on UDP port 123 and UDP port 53. (camouflaging as NTP and DNS). The port 53 traffic is distinctive as the UDP payload byte 8-9 are the country code after a geoIP lookup to maxmind. This is NSCount if it was DNS traffic, so by looking up country codes here we should have little chance for False Positives. One problem though the UDP payload is XORED so we need to find the corect country code.

Luckily I have made a script to generate the correct hex values:

So all we have to do then is create a signature that detects UDP port 53 traffic that has byte 8-9 set to our local country code. That should not hit performance to bad either. Alert for ZeroaAccess installation detected.

The UDP 123 traffic can be detected pretty much tha same way. UDP payload byte 0-1 will be 0x474e and the followeb by country code again. Once again XORED so we need to generate our country code:

Alert for ZeroAccess bot installation complete with UDP port 123 and the bytes given above that is correct for your environment.

That should reliably detect ZeroAccess installations.

2. Detect P2P update traffic

When the bot is up and running and want to keep its P2P list up to date it talks to ZeroAccess supernodes on UDP port 16464, 16465, 16470 or 16471. As we remember from the analysis it will be asking for P2P lists with the command getL. This is XORED with a different key but the values are static so we can simply just look for them in the packet.

Lets add that to the ports and we should be hitting bullseye with this signature as well. UDP payload byte 4-7 should look like 0x28948dab. Alert on ZeroAccess P2P activity.

That should take care of the installation part and update parts of the ZeroAccess bot.

Happy ZeroAccess detection