CryptoLocker is a type of malware that encrypts files on infected devices and demands a ransom payment in order to decrypt them. It has been around since 2013 and has impacted many individuals and organizations. But is CryptoLocker truly malware? Let’s take a closer look.
What is CryptoLocker?
CryptoLocker is a form of ransomware that is delivered most often via phishing emails containing infected attachments or links. When activated, it encrypts files on the infected device using strong encryption algorithms. A ransom note is displayed demanding payment, often in Bitcoin, in order to obtain the decryption key. If the ransom is not paid within a short timeframe, the decryption key is destroyed and the files remain locked forever.
The initial version of CryptoLocker was distributed from September 2013 until May 2014, when the botnet spreading it was taken down by law enforcement authorities. It resurfaced again in 2016 and numerous copycat versions have emerged since then. CryptoLocker has been used to target individuals as well as businesses, government agencies, and other organizations.
Key Characteristics of CryptoLocker
CryptoLocker has the following key characteristics that can help identify it:
- Encrypts files using RSA-2048 or AES-256 encryption that is practically unbreakable without the decryption key
- Searches connected drives and folders to encrypt files with certain extensions (e.g. .doc, .pdf, .jpg)
- Displays a ransom note demanding payment, often 0.5-2 Bitcoins
- Threatens permanent file destruction if ransom not paid rapidly (often 72 hours)
- Ransom payments go to difficult-to-trace Bitcoin addresses
- Exploits the Tor anonymity network to communicate with command servers
- Prevents infected computers from accessing certain antivirus vendor websites
Impact of CryptoLocker
The impact of CryptoLocker has been significant:
- Infected 2-3% of PCs during initial 2013 outbreak
- Made over $3 million in just first 100 days in 2013
- Cost businesses like MEGA, the operator of MegaUpload, around $35 million
- Forced police departments to pay ransom to decrypt case files
- Estimated total damages of $500 million+ to all infected parties
In addition to financial loss, CryptoLocker also causes major disruption and downtime for businesses and individuals when files are encrypted and inaccessible. Patient records, databases, contracts, and a wide range of other important data have been impacted.
CryptoLocker Uses Malware Tactics
CryptoLocker displays many typical characteristics of malware, including:
- Hiding its presence from the user and antivirus software
- Using encryption or obfuscation to evade detection
- Modifying Windows registry settings to ensure persistence after reboot
- Injecting itself into running processes like explorer.exe
- Using peer-to-peer command structures to avoid central servers
These stealth mechanisms allow CryptoLocker to reside undetected on infected systems, conducting malicious activities like file encryption or Bitcoin wallet theft in the background.
CryptoLocker Spreads Through Malware Tactics
In addition, CryptoLocker leverages classic malware tactics to spread itself:
- Phishing emails with rigged attachments
- Infected websites delivering malware payloads
- Malvertising and drive-by downloads
- Exploits targeting browser or software vulnerabilities
- Third party apps and tools containing malware bundles
By piggybacking on botnets and past malware infections, CryptoLocker exhibits traits of a virus looking to proliferate quickly across networks and devices.
CryptoLocker Functions Like Ransomware
CryptoLocker’s core functionality matches the definition of ransomware, a type of malware categorized by:
- Encrypting data to hold it “hostage”
- Demanding untraceable ransom payments from victims
- Threatening permanent data destruction if payment not received
- Targeting individuals, businesses, and organizations indiscriminately
Ransomware is considered a criminal business model and an evolution of malware development by cybersecurity experts worldwide.
CryptoLocker Exhibits Key Malware Behaviors
Based on analysis by security researchers, CryptoLocker displays the following behaviors that classify it as malware:
- Hijacks normal system processes and functions
- Steals or destroys data on infected devices
- Causes performance issues or disables security tools
- Connects to malicious domains for commands or updates
- Drops additional payloads to further compromise the system
- Transmits identifying information about the infected system
These behaviors allow CryptoLocker to carry out its ransom demands while maximizing damage, disruption, and self-propagation – all hallmarks of malicious software.
CryptoLocker Shares Code With Other Malware
Researchers have found code similarities between CryptoLocker and other known malware strains, suggesting shared infrastructure, resources, and techniques with broader cybercriminal operations.
Code reuse across malware families is a common tactic to avoid reinventing basic malware components. This further positions CryptoLocker among recognized malware threats.
CryptoLocker Uses Anti-Analysis Defenses
Sophisticated malware often employs anti-analysis defenses to avoid security researcher scrutiny. CryptoLocker exhibits several anti-analysis features:
- Detects virtual machines and sandbox environments
- Terminates processes when antivirus or debugging tools are detected
- Uses encryption and polymorphism to change signatures
- Resists reverse-engineering through code obfuscation
Using these techniques makes CryptoLocker harder to study, but is a hallmark of carefully crafted malware.
CryptoLocker Affiliates With Botnets
CryptoLocker has been spread through various botnet distributions channels, including:
- GameOver Zeus botnet
- Shylock banking trojan botnet
- Cutwail spam botnet
- Necurs spam botnet
Botnets are a popular malware mechanism, and CryptoLocker’s use of them cements its status as a cyberthreat.
CryptoLocker Uses Domain Generation Algorithms
CryptoLocker and its variants utilize domain generation algorithms (DGA) to randomly generate domain names for command and control servers. DGAs are primarily employed by malware to:
- Avoid using fixed server domains that can be blocked
- Frustrate security analysts and defenders
- Dynamically identify active command servers
The use of DGAs highlights the sophisticated coding behind CryptoLocker as advanced malware.
CryptoLocker Evades Security Defenses
CryptoLocker uses various tactics to evade detection and analysis by security solutions:
- Disabling Windows Update and antivirus services
- Closing security scanner and monitoring processes
- Blocking access to antivirus vendor websites
- Detecting analysis environments like sandboxes
- Using encryption and polymorphism to avoid signature detection
- Communicating over encrypted channels like Tor
These stealth measures allow CryptoLocker to operate undetected on systems with active endpoint or network security in place.
CryptoLocker Exploits Human Vulnerabilities
In addition to technical exploits, CryptoLocker also manipulates human vulnerabilities to increase infections:
- Targets user tendencies to open emails and attachments
- Delivers ransom notes designed to create urgency and fear
- Intimidates victims into paying ransoms through threats
- Takes advantage of user naivety about cybersecurity best practices
Exploiting human behaviors is a common and troubling malware technique.
CryptoLocker Can Spread Automatically
Like other malware, CryptoLocker can also spread automatically after an initial infection:
- Using built-in worming capabilities to scan and infect other devices
- Loading additional malware tools and frameworks
- Attacking network shares and resources
- Copying itself to removable media like USB drives
This autonomous propagation allows CryptoLocker to rapidly compromise entire systems and networks.
Conclusion
Based on analysis of its tactics, behaviors, and capabilities, security experts overwhelmingly agree that CryptoLocker exhibits all the hallmarks of malicious software or malware.
Key persuasive points include:
- Encrypting files and holding them for ransom matches ransomware behavior
- Spreading through phishing, exploits, and botnets is characteristic of malware
- Using malware techniques like DGAs and code obfuscation
- Disabling security tools and evading detection shows malware intent
- Stealing data, causing damage, and self-replicating autonomously
While ransomware displays some unique traits, CryptoLocker leverages the same critical tools, distribution vectors, infrastructure, and goals as more traditional malware forms like viruses, worms, and trojans.
Based on these shared mechanisms and behaviors, there is overwhelming evidence that CryptoLocker fits the classification as a destructive piece of malware.
Victims, businesses, and government institutions should treat CryptoLocker attacks with the same severity as other malware outbreaks. Protecting systems requires adapting many of the same security strategies used to block malware – like email scanning, system monitoring, and user education.
Understanding the sophisticated malware capabilities powering CryptoLocker highlights why it remains an ongoing cybersecurity threat, and helps organizations better prepare defenses against this crippling form of attack.