CryptoLocker Ransomware Infections

Systems Affected
Microsoft Windows systems running Windows 8, Windows 7, Vista, and XP operating systems

Description
CryptoLocker appears to have been spreading through fake emails designed to mimic the look of legitimate businesses and through phony FedEx and UPS tracking notices. In addition, there have been reports that some victims saw the malware appear following after a previous infection from one of several botnets frequently leveraged in the cyber-criminal underground.

Impact
The malware has the ability to find and encrypt files located within shared network drives, USB drives, external hard drives, network file shares and even some cloud storage drives. If one computer on a network becomes infected, mapped network drives could also become infected. CryptoLocker then connects to the attackers’ command and control (C2) server to deposit the asymmetric private encryption key out of the victim’s reach.

Victim files are encrypted using asymmetric encryption. Asymmetric encryption uses two different keys for encrypting and decrypting messages. Asymmetric encryption is a more secure form of encryption as only one party is aware of the private key, while both sides know the public key.

While victims are told they have three days to pay the attacker through a third-party payment method (MoneyPak, Bitcoin), some victims have claimed online that they paid the attackers and did not receive the promised decryption key.

Following preventative measures to protect computer networks from a CryptoLocker infection: 

• Do not follow unsolicited web links in email messages or submit any information to web pages in links 
• Use caution when opening email attachments. Refer to the Security Tip Using Caution with Email Attachments for more information on safely handling email attachments 
• Maintain up-to-date anti-virus software 
• Perform regular backups of all systems to limit the impact of data and/or system loss 
• Apply changes to your Intrusion Detection/Prevention Systems and Firewalls to detect any known malicious activity 
• Secure open-share drives by only allowing connections from authorized users 
• Keep your operating system and software up-to-date with the latest patches 
• Refer to the Recognizing and Avoiding Email Scams (pdf) document for more information on avoiding email scams 
• Refer to the Security Tip Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks 

Mitigation
Following possible mitigation steps that users and administrators can implement, if you believe your computer has been infected with CryptoLocker malware:

• Immediately disconnect the infected system from the wireless or wired network. This may prevent the malware from further encrypting any more files on the network 
• Users who are infected should change all passwords AFTER removing the malware from their system 
• Users who are infected with the malware should consult with a reputable security expert to assist in removing the malware, or users can retrieve encrypted files by the following methods: 
• Restore from backup, 
• Restore from a shadow copy or 
• Perform a system restore.

Source from: https://www.us-cert.gov/ncas/alerts/TA13-309A

Malicious Software and Security

There are many types of malicious software, outside of your typical viruses, attack systems every day. The following sections outline other types of malicious software but understand that they are all considered types of viruses.

Trojan horses
Trojan horses virus are special designed and bundled in an exe file, when some one click on this exe file then it executes the virus program and takes control of the system. For example, NetBus is a very popular Trojan virus that ships as a file called patch.exe. A hacker e-mails the file called patch.exe and explains in the e-mail that this is a security patch you need to apply to make sure your system is secure. Unfortunately, patch.exe is the security hole! When you run patch.exe, it opens your system up to the hacker by opening a port so that the hacker can connect to the port at any time and control your system. Trojan viruses are normally loaded on your system by the hacker tricking you into running the program on the system. You can remove the Trojan with virus-protection software.

Worms
A worm is a self-replicating virus. By self-replicating, I mean that the worm doesn't need to be activated by the user opening the file. A worm is a virus that runs on a system and also tries to infect other systems on the network. The Nimda virus is an example of a worm virus. Worms are loaded on your system by connecting to your system from across the Internet. The worm is usually designed to infect the system by connecting through a specific piece of software.

Spyware and adware
Spyware is software that loads on your system and then monitors your Internet activity, while adware is software that creates pop-ups from time to time advertising a particular product or service. Both of these types of viruses infect your system when you surf the wrong Internet site. Spyware and adware have become a huge negative result of the Internet, so a number of products are available to eliminate spyware and adware.

The most popular products used to eliminate spyware and adware are:

• Spybot Search & Destroy
• Ad-Aware
• Microsoft’s Windows Defender

Fake Antivirus Software

How Fake antivirus function?
Fake antivirus is malicious software (malware) designed to steal information from unsuspecting users by mimicking legitimate security software. The malware makes numerous system modifications making it extremely difficult to terminate unauthorized activities and remove the program. It also causes realistic, interactive security warnings to be displayed to the computer user.

How can my computer become infected with fake antivirus?
Criminals distribute this type of malware using search engines, emails, social networking sites, internet advertisements and other malware. They leverage advanced social engineering methodologies and popular technologies to maximize number of infected computers.

How will I know if I am infected?
The presence of pop-ups displaying unusual security warnings and asking for credit card or personal information is the most obvious method of identifying a fake antivirus infection.

What can I do to protect myself?

• Be cautious when visiting web links or opening attachments from unknown senders.
• Keep software patched and updated.
• To purchase or renew software subscriptions, visit the vendor sites directly.
• Monitor your credit cards for unauthorized activity.
• Report Internet crime or fraud immediately to law enforce agencies.