Last Updated: 2014-07-07 21:43:23 UTC
by Johannes Ullrich (Version: 1)
Thanks to reader Gary for sending us in a sample of a *Coin miner that he found attacking Port 32764. Port 32764 was recently found to offer yet another backdoor on Sercomm equipped devices. We covered this backdoor before 
The bot itself appears to be a variant of the "zollard" worm sean before by Symantec . Symantec's writeup describes the worm as attacking a php-cgi vulnerability, not the Sercomm backdoor. But this worm has been seen using various exploits.
Here some quick, very preliminary, details:
The reason I call it *Coin vs. Bitcoin is that in the past, we found these miners to mostly attack non-Bitcoin crypto-currencies to make use of the limited capabilities of these devices. I do not have sufficient detail yet about this variant.
Interestingly, Gary found what looks like 5 binaries with identical functionality, but compiled for 4 different architecture providing for larger coverage across possible vulnerable devices. The binaries are named according to the architecture they support.
|arm||86680||ELF 32-bit LSB executable, ARM, version 1, statically linked, stripped|
|armeabi||131812||ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, stripped|
|mips||140352||ELF 32-bit MSB executable, MIPS, MIPS-I version 1 (SYSV), statically linked, stripped|
|mipsel||141288||ELF 32-bit LSB executable, MIPS, MIPS-I version 1 (SYSV), statically linked, stripped|
|x86||74332||ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, stripped|
The binary appears to do the following among other things:
- delete and then recreate the /tmp directory (to have an empty one for download)
- create a directory /var/run/.zollard
- firewall port 23 (telnet) and 32764 (trying to avoid re-exploitation. Port 23 is odd ...)
- start the telnet demon (odd that it also firewalls port 23)
- it uses this user agent for some outbound requests: Mozilla/5.0 (compatible; Zollard; Linux)
- setup a php file with a backdoor (simple php "exec")
It also looks like there are many other variants for different architectures based on string in the file Gary sent us.