“Petya” Ransomware attack: What it is and how can it be stopped?


On June 27, 2017 reports of a ransomware infection began spreading across Europe. We saw the first infections in Ukraine, where more than 12,500 machines encountered the threat. We then observed infections in another 64 countries, including Belgium, Brazil, Germany, Russia, and the United States.
The new ransomware has worm capabilities, which allows it to move laterally across infected networks. Based on our investigation, this new ransomware shares similar codes and is a new variant of Ransom:Win32/Petya. This new strain of ransomware, however, is more sophisticated.
To protect our customers, we released cloud-delivered protection updates and made updates to our signature definition packages shortly after. These updates were automatically delivered to all Microsoft free antimalware products, including Windows Defender Antivirus and Microsoft Security Essentials. You can download the latest version of these files manually at the Malware Protection Center.
Windows Defender Advanced Threat Protection (Windows Defender ATP) automatically detects behaviors used by this new ransomware variant without any updates.


Like WannaCry, ‘Petya’ spreads rapidly through networks that use Microsoft Windows, but what is it, why is it happening and how can it be stopped?

How does it work?

When a computer is infected, the ransomware encrypts important documents and files and then demands a ransom, typically in Bitcoin, for a digital key needed to unlock the files. If victims don’t have a recent back-up of the files they must either pay the ransom or face losing all of their files.

How does the ‘Petya’ ransomware work?

The ransomware takes over computers and demands $300, paid in Bitcoin. The malicious software spreads rapidly across an organization once a computer is infected using the EternalBlue vulnerability in Microsoft Windows (Microsoft has released a patch, but not everyone will have installed it) or through two Windows administrative tools. The malware tries one option and if it doesn’t work, it tries the next one. “It has a better mechanism for spreading itself than WannaCry”, said Ryan Kalember, of cybersecurity company Proofpoint.

Is there any protection?

Most major antivirus companies now claim that their software has updated to actively detect and protect against ‘Petya’ infections: Symantec products using definitions version 20170627.009 should, for instance, and Kaspersky also says its security software is now capable of spotting the malware. Additionally, keeping Windows up to date – at the very least through installing March’s critical patch defending against the EternalBlue vulnerability – stops one major avenue of infection, and will also protect against future attacks with different payloads.
For this particular malware outbreak, another line of defence has been discovered: ‘Petya’ checks for a read-only file, C:\Windows\perfc.dat, and if it finds it, it won’t run the encryption side of the software. But this “vaccine”doesn’t actually prevent infection, and the malware will still use its foothold on your PC to try to spread to others on the same network.

Prevention

Use cloud protection to help guard against the latest malware threats. It’s turned on by default for Microsoft Security Essentials and Windows Defender Antivirus for Windows 10.
Go to Settings > Update & security > Windows Defender > Windows Defender Security Center > Virus & threat protection and make sure that your Cloud-based Protection settings is turned On.

Why is it called ‘Petya’?

Strictly speaking, it is not. The malware appears to share a significant amount of code with an older piece of ransomware that really was called Petya, but in the hours after the outbreak started, security researchers noticed that “the superficial resemblance is only skin deep”. Researchers at Russia’s Kaspersky Lab redubbed the malware NotPetya, and increasingly tongue-in-cheek variants of that name – Petna, Pneytna, and so on – began to spread as a result. On top of that, other researchers who independently spotted the malware gave it other names: Romanian’s Bitdefender called it Goldeneye, for instance.

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