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Petya? I hardly know ya! – an ISC update on the 2017-06-27 ransomware outbreak, (Wed, Jun 28th)

This is a follow-up the our previous diary on the ransomware outbreak that happened yesterday on Tuesday 2017-06-27.


By now, it seems almost everyone has written something about yesterdays ransomware outbreak. This led to some confusion after more information became available, and initial reports were updated. border-width:2px” />
Shown above: Screen shot from a host infected with this ransomware.

What we know so far

This ransomware targets systems running Microsoft Windows. Although initial reporting called this ransomware Petya or a Petya variant, Kaspersky researchers reported its a new ransomware. Kaspersky has been calling the malware NotPetya, and other names have been floating around for it. However, many people and organizations still call the ransomware Petya or a Petya variant.

This ransomware uses a modified version of the EternalBlue SMB exploit, and it also spreads using other methods like WMI commands, MimiKatz, and PSExec. Although exploits for EternalBlue are relatively recent, malware has been using file shares and WMI to spread for years, and these older techniques dont require any vulnerabilities.

During the infection process, this ransomware overwrites the MBR with a custom boot loader that implements a tiny malicious kernel. That tiny kernel encrypts the master file table (MFT) so the file system is unreadable. The result is an unbootable system that demands a ransom to restore it. border-width:2px” />
Shown above: Nearly 4 Bitcoin received for that Bitcoin wallet as of 2017-06-28 at 16:44 UTC.

Based on public reports, this attack appears to have originated in Ukraine. According to Krebs on Security the Ukrainian Cyber Police tweeted this attack may have started through a software update mechanism built into M.E.Doc, an accounting program used by companies working with the Ukrainian government. From the Ukraine, it spread to major European firms like Maersk.

Although weve seen some information on files related to this ransomware, we can only confirm two DLL files as samples of the actual ransomware. The SHA256 file hashes are:

How can you protect yourself against this threat? Steps include:

  • Deploy the latest Microsoft patches, especially MS17-010.
  • Consider disabling SMBv1.
  • Restrict who has local administrative access. Most people can operate with Standard User accounts instead of Administrator accounts.
  • If you have a large or complex infrastructure, segment your network.
  • Keep your anti-virus software up-to-date. Vendors are constantly updating definitions to cover the latest malware samples.

Most importantly, you should implement a solid backup and recovery procedure for your critical data, just in case the worst happens and you get infected.

Final words

The day after this ransomware attack, our initial excitement has died down a bit. Affected organizations are conducting response actions, and many others are implementing (or confirming) proper countermeasures.

We hope your organization is following best security practices and is protected against this latest threat.

Brad Duncan
brad [at]

(c) SANS Internet Storm Center. Creative Commons Attribution-Noncommercial 3.0 United States License.

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