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National Cyber Awareness System: TA14-295A: Crypto Ransomware
10/22/2014 05:28 PM EDT
Original release date: October 22, 2014
Systems Affected: Microsoft Windows
Ransomware is a type of malicious software (malware) that infects a computer and restricts access to it until a ransom is paid to unlock it. This
Alert is the result of Canadian Cyber Incident Response Centre (CCIRC) analysis in coordination with the United States Department of Homeland Security
(DHS) to provide further information about crypto ransomware, specifically to:
• Present its main characteristics, explain the prevalence of ransomware, and the proliferation of crypto ransomware variants; and
• Provide prevention and mitigation information.
WHAT IS RANSOMWARE?
Ransomware is a type of malware that infects a computer and restricts a user’s access to the infected computer. This type of malware, which has now
been observed for several years, attempts to extort money from victims by displaying an on-screen alert. These alerts often state that their computer
has been locked or that all of their files have been encrypted, and demand that a ransom is paid to restore access. This ransom is typically in the
range of $100–$300 dollars, and is sometimes demanded in virtual currency, such as Bitcoin.
Ransomware is typically spread through phishing emails that contain malicious attachments and drive-by downloading. Drive-by downloading occurs when a
user unknowingly visits an infected website and malware is downloaded and installed without their knowledge. Crypto ransomware, a variant that
encrypts files, is typically spread through similar methods, and has been spread through Web-based instant messaging applications.
WHY IS IT SO EFFECTIVE?
The authors of ransomware instill fear and panic into their victims, causing them to click on a link or pay a ransom, and inevitably become infected
with additional malware, including messages similar to those below:
• “Your computer has been infected with a virus. Click here to resolve the issue.”
• “Your computer was used to visit websites with illegal content. To unlock your computer, you must pay a $100 fine.”
• “All files on your computer have been encrypted. You must pay this ransom within 72 hours to regain access to your data.”
PROLIFERATION OF VARIANTS
In 2012, Symantec, using data from a command and control (C2) server of 5,700 computers compromised in one day, estimated that approximately 2.9
percent of those compromised users paid the ransom. With an average ransom of $200, this meant malicious actors profited $33,600 per day, or $394,400
per month, from a single C2 server. These rough estimates demonstrate how profitable ransomware can be for malicious actors.
This financial success has likely led to a proliferation of ransomware variants. In 2013, more destructive and lucrative ransomware variants were
introduced including Xorist, CryptorBit, and CryptoLocker. Some variants encrypt not just the files on the infected device but also the contents of
shared or networked drives. These variants are considered destructive because they encrypt user’s and organization’s files, and render them
useless until criminals receive a ransom.
Additional variants observed in 2014 included CryptoDefense and Cryptowall, which are also considered destructive. Reports indicate that CryptoDefense
and Cryptowall share the same code, and that only the name of malware itself is different. Similar to CryptoLocker, these variants also encrypt files
on the local computer, shared network files, and removable media.
LINKS TO OTHER TYPES OF MALWARE
Systems infected with ransomware are also often infected with other malware. In the case of CryptoLocker, a user typically becomes infected by opening
a malicious attachment from an email. This malicious attachment contains Upatre, a downloader, which infects the user with GameOver Zeus. GameOver
Zeus is a variant of the Zeus Trojan that steals banking information and is also used to steal other types of data. Once a system is infected with
GameOver Zeus, Upatre will also download CryptoLocker. Finally, CryptoLocker encrypts files on the infected system, and requests that a ransom be
The close ties between ransomware and other types of malware were demonstrated through the recent botnet disruption operation against GameOver Zeus,
which also proved effective against CryptoLocker. In June 2014, an international law enforcement operation successfully weakened the infrastructure of
both GameOver Zeus and CryptoLocker.
Ransomware doesn’t only target home users; businesses can also become infected with ransomware, which can have negative consequences, including:
• Temporary or permanent loss of sensitive or proprietary information;
• Disruption to regular operations;
• Financial losses incurred to restore systems and files; and
• Potential harm to an organization’s reputation.
Paying the ransom does not guarantee the encrypted files will be released; it only guarantees that the malicious actors receive the victim’s money,
and in some cases, their banking information. In addition, decrypting files does not mean the malware infection itself has been removed.
Infections can be devastating to an individual or organization, and recovery can be a difficult process that may require the services of a reputable
data recovery specialist.
US-CERT and CCIRC recommend users and administrators take the following preventive measures to protect their computer networks from ransomware
• Perform regular backups of all critical information to limit the impact of data or system loss and to help expedite the recovery process. Ideally,
this data should be kept on a separate device, and backups should be stored offline.
• Maintain up-to-date anti-virus software.
• Keep your operating system and software up-to-date with the latest patches.
• Do not follow unsolicited web links in email. Refer to the Security Tip Avoiding Social Engineering and Phishing Attacks for more information on
social engineering attacks.
• Use caution when opening email attachments. For information on safely handling email attachments, see Recognizing and Avoiding Email Scams.
• Follow safe practices when browsing the web. See Good Security Habits and Safeguarding Your Data for additional details.
Individuals or organizations are not encouraged to pay the ransom, as this does not guarantee files will be released. Report instances of fraud to the
FBI at the Internet Crime Complaint Center or contact the CCIRC .
• Kaspersky Lab, Kaspersky Lab detects mobile Trojan Svpeng: Financial malware with ransomware capabilities now targeting U.S.
• United States National Cybersecurity and Communications Integration Center, Cryptolocker Ransomware
• Sophos / Naked Security, What’s next for ransomware? CryptoWall picks up where CryptoLocker left off
• Symantec, CryptoDefence, the CryptoLocker Imitator, Makes Over $34,000 in One Month
• Symantec, Cryptolocker: A Thriving Menace
• Symantec, Cryptolocker Q&A: Menace of the Year
• Symantec, International Takedown Wounds Gameover Zeus Cybercrime Network