CryptoLocker: A particularly pernicious virus

Susan Bradley

Online attackers are using encryption to lock up our files and demand a ransom — and AV software probably won’t protect you.

Here are ways to defend yourself from CryptoLocker — pass this information along to friends, family, and business associates.

Forgive me if I sound a bit like those bogus virus warnings proclaiming, “You have the worst virus ever!!” But there’s a new threat to our data that we need to take seriously. It’s already hit many consumers and small businesses. Called CryptoLocker, this infection shows up in two ways.

First, you see a red banner (see Figure 1) on your computer system, warning that your files are now encrypted — and if you send money to a given email address, access to your files will be restored to you.

CryptoLocker warning

Figure 1. CryptoLocker is not making idle threats.

The other sign you’ve been hit: you can no longer open Office files, database files, and most other common documents on your system. When you try to do so, you get another warning, such as “Excel cannot open the file [filename] because the file format or file extension is not valid,” as stated on a TechNet MS Excel Support Team blog.

As noted in a Reddit comment, CryptoLocker goes after dozens of file types such as .doc, .xls, .ppt, .pst, .dwg, .rtf, .dbf, .psd, .raw, and .pdf.

CryptoLocker attacks typically come in three ways:

1) Via an email attachment. For example, you receive an email from a shipping company you do business with. Attached to the email is a .zip file. Opening the attachment launches a virus that finds and encrypts all files you have access to — including those located on any attached drives or mapped network drives.

2) You browse a malicious website that exploits vulnerabilities in an out-of-date version of Java.

3) Most recently, you’re tricked into downloading a malicious video driver or codec file.

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All Windows Secrets articles posted on 2013-10-24:

Susan Bradley

About Susan Bradley

Susan Bradley is a Small Business Server and Security MVP, a title awarded by Microsoft to independent experts who do not work for the company. She's also a partner in a California CPA firm.