Introduction At the end of January 2017, BleepingComputer published a report about an updated variant of CryptoMix (CryptFile2) ransomware calling itself CryptoShield [1]. It was first discovered by Proofpoint security researcher Kafeine. At that time, CryptoShield was distributed by the EITest campaign using Rig exploit kit (EK). Since then, other researchers continued seeing CryptoShield from EITest Rig EK. I've already documented this Rig EK/CryptoShield combo twice [2, 3], and it shows no signs of stopping. With that in mind, let's look at a recent infection generated on Wednesday, 2017-02-08. Traffic As I've stated before, EK traffic is kicked off by some sort of referer, usually by a compromised website or a malicious online ad (malvertisement) that has injected code leading to an EK landing page [4].
I tried the site and saw injected EITest script leading to a Rig EK landing page. Approximately 35 minutes later, I tried it again and saw a different Rig EK domain using the same IP address.
Shortly after viewing the site, the Windows host was infected. I first saw an application error, then received a User Account Control (UAC) notification. After clicking through those two popup notifications, the host was fully infected. The infected Windows host then showed indicators of CryptoShield. Both a browser window and a text file appeared on the desktop, and they showed the decryption instructions.
Malware CryptoShield uses .CRYPTOSHIELD as the suffix for any files it encrypts. Based on the HTML file, the sample I saw (the same sample during both infections) was version 1.1 of the ransomware. This CryptoShield sample set itself up for persistence in the Windows registry under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run.
Indicators of compromise (IOCs) Rig EK IP address and domains:
Post infection traffic from the CryptoShield sample:
File information for the Rig EK Flash exploit:
File information for the Rig EK payload:
Final words Thanks to the people on Twitter who tweet information about compromised websites leading to Rig EK. Without help from the community, this type of traffic would be much harder to obtain. Rig EK has been around for a while. I wrote a diary about Rig EK back in April 2015, and Rig EK was active well before then. As always, if you follow best security practices (keep your Windows computer up-to-date and patched), your risk of infection is minimal. Unfortunately, not enough people follow best practices, so it apparently remains profitable for criminals to continue using Rig EK as a method of malware distribution. For now, CryptoShield ransomware from Rig EK remains a continuing presence in our threat landscape. Pcaps, malware, and artifacts for this diary are available here. --- References: [1] https://www.bleepingcomputer.com/news/security/cryptomix-variant-named-cryptoshield-1-0-ransomware-distributed-by-exploit-kits/ |
Brad 394 Posts ISC Handler Feb 9th 2017 |
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Feb 9th 2017 4 years ago |
Quote:Shortly after viewing the site, the Windows host was infected. I first saw an application error, then received a User Account Control (UAC) notification. After clicking through those two popup notifications, the host was fully infected. How does the infection happen, i.e. what is the EXACT attack vector? 1. to display this FAKE "application error" dialog box the attacker needs to escape from (the confines of) the browser and run native code which calls MessageBox(). 2. to have the UAC prompt displayed the attacker also needs to escape from the browser and run native code which calls ShellExecute() Have you recorded the command line(s) used to start the attackers code? See https://technet.microsoft.com/en-us/library/3004375.aspx alias https://support.microsoft.com/en-us/kb/3004375 JFTR: if this CryptoCrap writes an executable to disk and tries to execute it (as they ALL do), it's HARMLESS: just use SAFER alias Software Restriction Policies to disable execution outside of %SystemRoot% and %ProgramFiles% and exercise strict privilege separation. |
Anonymous |
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Feb 9th 2017 4 years ago |
Quote:Pcaps, malware, and artifacts for this diary are available here. "Here" alias http://www.malware-traffic-analysis.net/2019/02/09/index.html yields HTTP error 404 |
Anonymous |
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Feb 9th 2017 4 years ago |
Thanks for the heads up. I fixed the link, and it should point to the proper page.
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Brad 394 Posts ISC Handler |
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Feb 9th 2017 4 years ago |
Can we get some sort of flag on each entry indicating the vulnerable and/or affected operating systems?
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Anonymous |
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Feb 9th 2017 4 years ago |
I am the guy this happened to, they also accessed my godaddy
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Anonymous |
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Mar 25th 2017 3 years ago |
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