Last Updated: 2015-11-06 02:03:39 UTC
by Brad Duncan (Version: 1)
2015-11-05 update: After posting this diary, we started seeing reports of CryptoWall 4.0. One of the people who analyzed this new CryptoWall variant provided me details, which you can read about at: http://malware-traffic-analysis.net/2015/11/05/index2.html
Since Monday 2015-10-26, we've noticed a particular campaign sending malicious spam (malspam) with links to download CryptoWall 3.0 ransomware. This campaign has been impersonating domain registrars. Conrad Longmore blogged about it last week , and Techhelplist.com has a good write-up on the campaign . Several other sources have also discussed this wave of malspam [3, 4, 5, 6, 7, 8 to name a few].
For this diary, we'll take a closer look at the emails and associated CryptoWall 3.0 malware.
Based on what I've seen, this malspam was delivered to recipients who didn't use privacy protection when they registered their domains. Their contact information is publicly-listed in the whois records for their domains. Criminals behind the campaign are collecting this publicly-available information, impersonating the registrars, and sending malspam to the email addresses listed as points of contact. Below are two examples of the emails I've found.
Enom and Tucows are just two of the many examples people have reported. When looking at the email headers, you'll find these were not sent from the actual registrars. The sender addresses were spoofed.
If you receive one of the emails, the link follows a specific pattern: http://[unrelated compromised website]/abuse_report.php?[your domain name]. The domain names are not important. You can always get the malware by substituting any string of characters for the domain name in the URL (assuming no one has fixed the compromised website yet).
The emails have different senders, and they contain a variety of domains in the URLs to download the malware. I've compiled a list of the first 100 emails I found to provide an idea on the scope of this campaign. Click here for a .CSV file of the list.
I grabbed a sample of the CryptoWall 3.0 on Tuesday 2015-11-03. The sample was first submitted to Virus Total the previous day (Monday).
File name: [domain name]_copy_of_complaints.pdf.scr
- File size: 223.0 KB ( 228,354 bytes )
- MD5 hash: 866f551ac050ce293bddfca62110d35a
- SHA1 hash: f11dcc4069e86d09f4b8a5a37a3a56756391ea40
- SHA256 hash: 02f61cebe546041985f4dac3ad6cee83c4cdc6511ec265dc78afcd69c8ac46a9
- First submitted to VirusTotal: 2015-11-02 20:17:03 UTC
- Detection ratio: 25 / 55
- VirusTotal Link - Malwr.com link - Hybrid-Analysis.com link
I ran the sample on two different Windows hosts and got two different Bitcoin addresses for the ransom payment.
Traffic from the two infected hosts is consistent with CryptoWall 3.0 activity.
If you receive one of these emails, and you download the file, you should see plenty of warnings the file is not safe. In a company environment, properly-administered Windows hosts should prevent people from running the malware.
In my personal opinion, this malspam isn't a serious threat, especially to anyone aware of computer security. So why do criminals run these campaigns? Apparently, enough of their emails get through, people still fall for the malware, and their Windows computers are configured so they can run it.
As of Wednesday 2015-11-04, I haven't found any more of this malspam. This might be temporary, or the criminals behind it might have started a different campaign. Either way, it's always interesting to see the daily changes in our cyber threat landscape.
Pcaps and the malware sample used in this diary are available here.