CryptoDefense

The recently-identified CryptoDefense is a file encryptor Trojan that encrypts popular file formats on the infected PC, causing the associated files to become unusable. Although this damage is, in theory, reversible, the hundreds of dollars in ransom that CryptoDefense demands for decrypting your files is an overly expensive solution that malware researchers would suggest you avoid paying. Instead, you should restore any affected files from a remote backup, if necessary, after using standardized anti-malware techniques and software to remove CryptoDefense from your computer.

The Ransomware that's Easier to Avoid Than Remove

CryptoDefense is a 2014-era Trojan that uses file-encrypting attacks to hold your files hostage, after which CryptoDefense insists on a heavy fee being paid to re-allow access to them. Malware experts have observed major CryptoDefense distribution methods leaning on the use of fraudulent Flash updates, media player updates and similar exploits, which can be blocked with strong security settings and software designed to disable browser-based attacks. They may be found on poorly-secured advertising networks, corrupted websites designed to look like streaming media domains and, occasionally, hacked websites.

Although it shouldn't be difficult to avoid CryptoDefense's infection vectors, once CryptoDefense's compromised your PC, CryptoDefense will use a RSA-2048 encryption system to 'scramble' the contents of common files, such as TXT, JPG or MP3. The complexity of this form of encryption means that, until now, there are no known tools for decrypting the attack freely. CryptoDefense also deletes the automatic file copies created on a daily basis by the Windows VSS (or Volume Shadow Copy Service). This makes it effectively impossible to restore your files, unless you have a remote backup on a secondary hard drive (such as any USB device) that hasn't been compromised by CryptoDefense.

Of course, CryptoDefense also is a 'business', and, as such, will try to extort money by placing text instructions for paying its ransom on your hard drive. This file, How_Decrypt.txt, suggests installing the 'Tor' Web browser, an 'anonymity network' program, and then commencing with a BitCoin-based payment to a Web address that's concealed through a proxy service. However, malware researchers warn that there are no guarantees that any decryption keys will be provided by CryptoDefense's creators, even if you do submit to their demands, which is why alternate solutions always are encouraged.

A Practical Defense Against the Latest in CryptoDefense Trojans

Although its attacks hardly are new to malware analysts, CryptoDefense's recent development is just a sample of how new threats can make use of old, but still effective attacks to harm PCs. As usual, the delivery system is CryptoDefense's greatest weak point, and PCs that avoid unsafe websites, scan files before launching them and have up-to-date anti-malware protection are at less risk from CryptoDefense installations than unprotected machines. Another important factor in crippling CryptoDefense's ransom attempt is the potential for keeping remote backups of critical files, which will let you restore them easily in the event of attacks by CryptoDefense or other threatening software.

CryptoDefense also is an example of how ostensibly beneficial technologies may be used for harmful actions. This isn't the first time malware experts have noted threats making use of BitCoins as a favored transaction method, and CryptoDefense isn't the first Trojan to abuse Tor privacy features for protecting cybercrooks. However, your own anti-malware technology should be up to removing CryptoDefense as needed, assuming that you take all appropriate defensive steps before scanning your PC. Thorough scans of any compromised PC especially are recommended to counter the potential for other threats being installed with CryptoDefense, which has been seen accompanied by adware and even other kinds of file encryptors.

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