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Ransomware

Ransomware stops you from using your PC. It holds your PC or files for "ransom". This page describes what ransomware is and what it does, and provides advice on how to prevent and recover from ransomware infections.

You can also read our blog about ransomware: The 5Ws and 1H of ransomware

On this page:


What does ransomware do?

There are different types of ransomware. However, all of them will prevent you from using your PC normally, and they will all ask you to do something before you can use your PC.

They can target any PC users, whether it’s a home computer, endpoints in an enterprise network, or servers used by a government agency or healthcare provider.

Ransomware can:

  • Prevent you from accessing Windows.

  • Encrypt files so you can't use them.

  • Stop certain apps from running (like your web browser).

Ransomware will demand that you pay money (a “ransom”) to get access to your PC or files. We have also seen them make you complete surveys.

There is no guarantee that paying the fine or doing what the ransomware tells you will give access to your PC or files again.


Frequently asked questions

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Details for home users

There are two types of ransomware – lockscreen ransomware and encryption ransomware.

Lockscreen ransomware shows a full-screen message that prevents you from accessing your PC or files. It says you have to pay money (a “ransom”) to get access to your PC again.

Encryption ransomware changes your files so you can’t open them. It does this by encrypting the files – see the Details for enterprises section if you’re interested in the technologies and techniques we’ve seen.

Older versions of ransom usually claim you have done something illegal with your PC, and that you are being fined by a police force or government agency.

These claims are false. It is a scare tactic designed to make you pay the money without telling anyone who might be able to restore your PC.

Newer versions encrypt the files on your PC so you can’t access them, and then simply demand money to restore your files.

Ransomware can get on your PC from nearly any source that any other malware (including viruses) can come from. This includes:

  • Visiting unsafe, suspicious, or fake websites.
  • Opening emails and email attachments from people you don’t know, or that you weren’t expecting.

  • Clicking on malicious or bad links in emails, Facebook, Twitter, and other social media posts, instant messenger chats, like Skype.

It can be very difficult to restore your PC after a ransomware attack – especially if it’s infected by encryption ransomware.

That’s why the best solution to ransomware is to be safe on the Internet and with emails and online chat:

  • Don’t click on a link on a webpage, in an email, or in a chat message unless you absolutely trust the page or sender.

  • If you’re ever unsure – don’t click it!

  • Often fake emails and webpages have bad spelling, or just look unusual. Look out for strange spellings of company names (like “PayePal” instead of “PayPal”) or unusual spaces, symbols, or punctuation (like “iTunesCustomer Service” instead of “iTunes Customer Service”).

Check our frequently asked questions for more information about ransomware, including troubleshooting tips in case you’re infected, and how you can backup your files to help protect yourself from ransomware.


Details for enterprises and IT professionals

The number of enterprise victims being targeted by ransomware is increasing. Usually, the attackers specifically research and target a victim (similar to whale-phishing or spear-phishing – and these in fact may be techniques used to gain access to the network).

The sensitive files are encrypted, and large amounts of money are demanded to restore the files. Generally, the attacker has a list of file extensions or folder locations that the ransomware will target for encryption.

Due to the encryption of the files, it can be practically impossible to reverse-engineer the encryption or “crack” the files without the original encryption key – which only the attackers will have access to.

The best advice for prevention is to ensure company-confidential, sensitive, or important files are securely backed up in a remote, un-connected backup or storage facility.

OneDrive for Business can assist in backing up everyday files.
In some cases, third-party tools released by some security firms are able to decrypt files for some specifically ransomware families. See our blog FireEye and Fox-IT tool can help recover Crilock-encrypted files for an example. Tim Rains, Microsoft Director of Security, released the blog Ransomware: Understanding the risk in April 2016 that summarizes the state of ransomware and provides statistics, details, and preventative suggestions to enterprises and IT professionals: Our Threat intelligence report: Ransomware also includes suggestions on prevention and recovery, statistics, and details.

How big is the ransomware problem?

Ransomware is a global problem. The US, Italy, Russia, Korea, and Spain saw the most ransomware encounters in 2016.

After exploding in the past couple of years, ransomware encounters seem to have begun to decline. However, this trend is not a reflection of the email and exploit kit campaigns that try to install ransomware on computers. Rather, it is a sign of better blocking of attacks by security software like Windows Defender Antivirus. All in all, millions of computers still encountered ransomware in 2016.

We’re still seeing significant amounts of email that carry ransomware downloaders. A total of 500M of these emails are being sent out every quarter. The email attachments reach millions of computers, but a lot of them are blocked from downloading and executing ransomware.

In 2016, we tracked over 200 ransomware families. Over half of these families were discovered only in 2016, which means that cybercriminals are constantly releasing new ransomware in the wild. Cerber and Locky were the most prominent ransomware families in 2016.

Top ransomware

  • Ransom:Win32/Cerber
  • Ransom:Win32/Locky
  • Ransom:Win32/Spora
  • Ransom:Win32/HydraCrypt
  • Ransom:Win32/Critroni
  • Ransom:Win32/Teerac
  • Ransom:Win32/Troldesh
Examples of ransomware
Ransom:Win32/Adslock.A
Ransom:Win32/Cribit.A
Ransom:Win32/Crilock.A