decrypt-lock
What happens when a computer is infected with the malicious software or a virus, and what should you do to protect your files?

Cryptolocker is back in the headlines, thanks to a coordinated effort to take down the computers and criminals that run the notorious “ransomware”. But what is it? And how can you fight it? 

Cryptolocker is ransomware: malicious software which holds your files to ransom

The software is typically spread through infected attachments to emails, or as a secondary infection on computers which are already affected by viruses which offer a back door for further attacks.

When a computer is infected, it contacts a central server for the information it needs to activate, and then begins encrypting files on the infected computer with that information. Once all the files are encrypted, it posts a message asking for payment to decrypt the files – and threatens to destroy the information if it doesn’t get paid.

The authorities have won users a two-week window of safety

The National Crime Agency (NCA) announced yesterday that the UK public has got a “unique, two-week opportunity to rid and safeguard” themselves from Cryptolocker. The agency didn’t go into more detail, but it seems likely that at least one of the central servers which Cryptolocker speaks to before encrypting files has been taken down.

The NCA has also taken down the control system for a related piece of software, known as GameOver Zeus, which provides criminals with a backdoor into users’ computers. That back door is one of the ways a computer can be infected with Cryptolocker in the first place.

What that means is, until the window is closed – and the virus cycles to new servers – users who are infected with Cryptolocker won’t lose their files to encryption. As a result, these users have the chance to remove the virus before it destroys data, using conventional anti-virus software. In other words, there has never been a better time to update the protection on your computer.

But watch out – while the servers that control Cryptolocker are out of action, it’s possible to be infected with it and not know. If you don’t keep your computer clean, then at the end of the two-week period, you could be in for a nasty surprise.

Cryptolocker only infects PCs, but there are other types of ransomware

Cryptolocker is the name of one particular virus, which only infects Windows PCs, running XP, Vista, Windows 7 or Windows 8. So if you use an Apple computer, it can’t affect you. Similarly, smartphones are safe from cryptolocker.

Although it is the most famous example of ransomware, it’s not the only one. Even in the two-week window, PC users may be infected with other types of ransomware, and Android and Mac OS users should carry on with their normal security precautions. Being safe from one type of malware doesn’t mean you’re safe from all of them.

If you’ve been infected by Cryptolocker, your files really are gone unless you have a backup

Some ransomware is little more than a confidence trickster, presenting a message asking for payment without having done anything to the user’s files. Cryptolocker isn’t like that: the software really does encrypt your files, to a strength which renders it unbreakable even by the fastest computers in the world – even if they had the entire lifetime of the universe to work on it.

That means you’ll have to rely on any backups of your data to get it back. But it’s important that you don’t try and restore your data before you clear your computer of the infection, otherwise you could lose your backup, too.

Sometimes paying the ransom will work, sometimes it won’t

Except, of course, there is another possibility. Some users hit with Cryptolocker report that they really did get their data back after paying the ransom – which is typically around £300. But there’s no guarantee it will work, because cybercriminals aren’t exactly the most trustworthy group of people.

What’s more, if the NCA really is bringing down the command and control servers, then the criminals may not be able to return the data, even if the ransom has been paid. There’s also a whole load of viruses which go out of their way to look like Cryptolocker, and which won’t hand back the data if victims pay. Plus, there’s the ethical issue: paying the ransom funds more crime.
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