11/12/2015
14:45

New variant Trojan.Win32.CryptoFF.C that encrypts document file.

This variant of ransomware encrypts all documents and rename their with extension ".1999", asking a ransom to unlock.

On December 11th, 2015, a new variant of ransomware crypto-malware Trojan.Win32.CryptoFF.A was discovered.
This new variant is called Trojan.Win32.CryptoFF.C  and is very similar to Trojan.Win32.CryptoFF.A.

The file analyzed "216.tmp" was found in the temporary folder of a computer hit by Trojan.Win32.CryptoFF.C
We don't have any more information as this malware spreads.


File name: 216.tmp
MD5: efb80d07d49ca43d53eb8eb9cd97ce21
Size: 203264 byte
Time Stamp (header): 10/12/2015 - 22.29.17

When running the Trojan.Win32.CryptoFF.C,  it immediately starts to encrypt the files.

When it finds the first victim, it will do the following things:

1) open the document
2) encrypt the document
3) rename the original file with extension ".1999" (e.g.  mydocument.doc -> mydocument.doc.1999)

The first 64 KB of files will be encrypted by Trojan.Win32.CryptoFF.C
If size of file is below 64 KB, then whole document will be encrypted.

The malware uses AES 256 bit to encrypt the files.
Inside the malware there is a bug when it encrypts file with size below 64 KB, in this case the decrypt of these files makes documents corrupted at end of files.


In each folder it will create 2 files:
SECRETISHERE.KEY (size: 1368 byte)
HELLOTHERE.TXT (size: 1015 byte)

The file "SECRETISHERE.KEY" contains a key in UUencode, after it's decoded, it will obtain a key of 1024 byte.
The file "HELLOTHERE.TXT" contains instructions to recover the file encrypted:

Hello.
All your files have been encrypted using our extremely strong private key. There is no way to recover them without our assistance. If you want to get your files back, you must be ready to pay for them. If you are ready to pay, then get in touch with us using a secure and anonymous p2p messenger. We have to use a messenger, because standard emails get blocked quickly and if our email gets blocked your files will be lost forever. So…
 
Go to http://bitmessage.org/, download and run Bitmessage. Click Your Identities tab, then click New, then click OK. Then click Send tab.
 
TO: BM-NByDti9xJ9NcFShLaBfE1fkAW8uk51WQ
SUBJECT: name of your PC or your IP address.
MESSAGE:  Hi, I am ready to pay.
 
Click Send button.
 
You are done.
 
To get the fastest reply from us with all further instructions, please keep your Bitmessage running on the computer all the time, if possible. If you cooperate and follow the instructions, you will get all your files back intact and very, very soon. Thank you.

When Trojan.Win32.CryptoFF.C will terminate to encrypt all document, it will show this image:

Image of Trojan.Win32.CryptoFF.C


The Trojan.Win32.CryptoFF.C removes the volume shadow copies with this command:
cmd.exe /Q /C vssadmin.exe delete shadows /all /quiet


Clean:
VirIT version 8.0.66 and later.


Analysis by eng. Gianfranco Tonello
C.R.A.M. (Anti-Malware Research Center) by TG Soft
Any information published on our site may be used and published on other websites, blogs, forums, facebook and/or in any other form both in paper and electronic form as long as the source is always and in any case cited explicitly “Source: CRAM by TG Soft www.tgsoft.it” with a clickable link to the original information and / or web page from which textual content, ideas and / or images have been extrapolated.
It will be appreciated in case of use of the information of C.R.A.M. by TG Soft www.tgsoft.it in the report of summary articles the following acknowledgment/thanks “Thanks to Anti-Malware Research Center C.R.A.M. by TG Soft of which we point out the direct link to the original information: [direct clickable link]”

Vir.IT eXplorer PRO is certified by the biggest international organisation: