Cryptovirology

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Cryptovirology refers to the study of cryptography use in malware, such as ransomware and asymmetric backdoors.[ citation needed ] Traditionally, cryptography and its applications are defensive in nature, and provide privacy, authentication, and security to users. Cryptovirology employs a twist on cryptography, showing that it can also be used offensively. It can be used to mount extortion based attacks that cause loss of access to information, loss of confidentiality, and information leakage, tasks which cryptography typically prevents. [1]

Contents

The field was born with the observation that public-key cryptography can be used to break the symmetry between what an antivirus analyst sees regarding malware and what the attacker sees. The antivirus analyst sees a public key contained in the malware, whereas the attacker sees the public key contained in the malware as well as the corresponding private key (outside the malware) since the attacker created the key pair for the attack. The public key allows the malware to perform trapdoor one-way operations on the victim's computer that only the attacker can undo.

Overview

The field encompasses covert malware attacks in which the attacker securely steals private information such as symmetric keys, private keys, PRNG state, and the victim's data. Examples of such covert attacks are asymmetric backdoors. An asymmetric backdoor is a backdoor (e.g., in a cryptosystem) that can be used only by the attacker, even after it is found. This contrasts with the traditional backdoor that is symmetric, i.e., anyone that finds it can use it. Kleptography, a subfield of cryptovirology, is the study of asymmetric backdoors in key generation algorithms, digital signature algorithms, key exchanges, pseudorandom number generators, encryption algorithms, and other cryptographic algorithms. The NIST Dual EC DRBG random bit generator has an asymmetric backdoor in it. The EC-DRBG algorithm utilizes the discrete-log kleptogram from kleptography, which by definition makes the EC-DRBG a cryptotrojan. Like ransomware, the EC-DRBG cryptotrojan contains and uses the attacker's public key to attack the host system. The cryptographer Ari Juels indicated that NSA effectively orchestrated a kleptographic attack on users of the Dual EC DRBG pseudorandom number generation algorithm and that, although security professionals and developers have been testing and implementing kleptographic attacks since 1996, "you would be hard-pressed to find one in actual use until now." [2] Due to public outcry about this cryptovirology attack, NIST rescinded the EC-DRBG algorithm from the NIST SP 800-90 standard. [3]

Covert information leakage attacks carried out by cryptoviruses, cryptotrojans, and cryptoworms that, by definition, contain and use the public key of the attacker is a major theme in cryptovirology. In "deniable password snatching," a cryptovirus installs a cryptotrojan that asymmetrically encrypts host data and covertly broadcasts it. This makes it available to everyone, noticeable by no one (except the attacker),[ citation needed ] and only decipherable by the attacker. An attacker caught installing the cryptotrojan claims to be a virus victim.[ citation needed ] An attacker observed receiving the covert asymmetric broadcast is one of the thousands, if not millions of receivers, and exhibits no identifying information whatsoever. The cryptovirology attack achieves "end-to-end deniability." It is a covert asymmetric broadcast of the victim's data. Cryptovirology also encompasses the use of private information retrieval (PIR) to allow cryptoviruses to search for and steal host data without revealing the data searched for even when the cryptotrojan is under constant surveillance. [4] By definition, such a cryptovirus carries within its own coding sequence the query of the attacker and the necessary PIR logic to apply the query to host systems.

History

The first cryptovirology attack and discussion of the concept was by Adam L. Young and Moti Yung, at the time called "cryptoviral extortion" and it was presented at the 1996 IEEE Security & Privacy conference. [1] [5] In this attack, a cryptovirus, cryptoworm, or cryptotrojan contains the public key of the attacker and hybrid encrypts the victim's files. The malware prompts the user to send the asymmetric ciphertext to the attacker who will decipher it and return the symmetric decryption key it contains for a fee. The victim needs the symmetric key to decrypt the encrypted files if there is no way to recover the original files (e.g., from backups). The 1996 IEEE paper predicted that cryptoviral extortion attackers would one day demand e-money, long before Bitcoin even existed. Many years later, the media relabeled cryptoviral extortion as ransomware. In 2016, cryptovirology attacks on healthcare providers reached epidemic levels, prompting the U.S. Department of Health and Human Services to issue a Fact Sheet on Ransomware and HIPAA. [6] The fact sheet states that when electronic protected health information is encrypted by ransomware, a breach has occurred, and the attack therefore constitutes a disclosure that is not permitted under HIPAA, the rationale being that an adversary has taken control of the information. Sensitive data might never leave the victim organization, but the break-in may have allowed data to be sent out undetected. California enacted a law that defines the introduction of ransomware into a computer system with the intent of extortion as being against the law. [7]

Examples

Tremor virus

While viruses in the wild have used cryptography in the past, the only purpose of such usage of cryptography was to avoid detection by antivirus software. For example, the tremor virus [8] used polymorphism as a defensive technique in an attempt to avoid detection by anti-virus software. Though cryptography does assist in such cases to enhance the longevity of a virus, the capabilities of cryptography are not used in the payload. The One-half virus was amongst the first viruses known to have encrypted affected files.

Tro_Ransom.A virus

An example of a virus that informs the owner of the infected machine to pay a ransom is the virus nicknamed Tro_Ransom.A. [9] This virus asks the owner of the infected machine to send $10.99 to a given account through Western Union.
Virus.Win32.Gpcode.ag is a classic cryptovirus. [10] This virus partially uses a version of 660-bit RSA and encrypts files with many different extensions. It instructs the owner of the machine to email a given mail ID if the owner desires the decryptor. If contacted by email, the user will be asked to pay a certain amount as ransom in return for the decryptor.

CAPI

It has been demonstrated that using just 8 different calls to Microsoft's Cryptographic API (CAPI), a cryptovirus can satisfy all its encryption needs. [11]

Other uses of cryptography-enabled malware

Apart from cryptoviral extortion, there are other potential uses of cryptoviruses, [4] such as deniable password snatching, cryptocounters, private information retrieval, and in secure communication between different instances of a distributed cryptovirus.

See also

Related Research Articles

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A cryptographically secure pseudorandom number generator (CSPRNG) or cryptographic pseudorandom number generator (CPRNG) is a pseudorandom number generator (PRNG) with properties that make it suitable for use in cryptography. It is also loosely known as a cryptographic random number generator (CRNG).

<span class="mw-page-title-main">RSA Security</span> American computer security company

RSA Security LLC, formerly RSA Security, Inc. and trade name RSA, is an American computer and network security company with a focus on encryption and encryption standards. RSA was named after the initials of its co-founders, Ron Rivest, Adi Shamir and Leonard Adleman, after whom the RSA public key cryptography algorithm was also named. Among its products is the SecurID authentication token. The BSAFE cryptography libraries were also initially owned by RSA. RSA is known for incorporating backdoors developed by the NSA in its products. It also organizes the annual RSA Conference, an information security conference.

A backdoor is a typically covert method of bypassing normal authentication or encryption in a computer, product, embedded device, or its embodiment. Backdoors are most often used for securing remote access to a computer, or obtaining access to plaintext in cryptosystems. From there it may be used to gain access to privileged information like passwords, corrupt or delete data on hard drives, or transfer information within autoschediastic networks.

Internet security is a branch of computer security. It encompasses the Internet, browser security, web site security, and network security as it applies to other applications or operating systems as a whole. Its objective is to establish rules and measures to use against attacks over the Internet. The Internet is an inherently insecure channel for information exchange, with high risk of intrusion or fraud, such as phishing, online viruses, trojans, ransomware and worms.

The security of cryptographic systems depends on some secret data that is known to authorized persons but unknown and unpredictable to others. To achieve this unpredictability, some randomization is typically employed. Modern cryptographic protocols often require frequent generation of random quantities. Cryptographic attacks that subvert or exploit weaknesses in this process are known as random number generator attacks.

Kleptography is the study of stealing information securely and subliminally. The term was introduced by Adam Young and Moti Yung in the Proceedings of Advances in Cryptology – Crypto '96. Kleptography is a subfield of cryptovirology and is a natural extension of the theory of subliminal channels that was pioneered by Gus Simmons while at Sandia National Laboratory. A kleptographic backdoor is synonymously referred to as an asymmetric backdoor. Kleptography encompasses secure and covert communications through cryptosystems and cryptographic protocols. This is reminiscent of, but not the same as steganography that studies covert communications through graphics, video, digital audio data, and so forth.

Ransomware is a type of cryptovirological malware that permanently block access to the victim's personal data unless a ransom is paid. While some simple ransomware may lock the system without damaging any files, more advanced malware uses a technique called cryptoviral extortion. It encrypts the victim's files, making them inaccessible, and demands a ransom payment to decrypt them. In a properly implemented cryptoviral extortion attack, recovering the files without the decryption key is an intractable problem, and difficult-to-trace digital currencies such as paysafecard or Bitcoin and other cryptocurrencies are used for the ransoms, making tracing and prosecuting the perpetrators difficult.

<span class="mw-page-title-main">AIDS (Trojan horse)</span> Early example of ransomware

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Dual_EC_DRBG is an algorithm that was presented as a cryptographically secure pseudorandom number generator (CSPRNG) using methods in elliptic curve cryptography. Despite wide public criticism, including the public identification of the possibility that the National Security Agency put a backdoor into a recommended implementation, it was for seven years one of four CSPRNGs standardized in NIST SP 800-90A as originally published circa June 2006, until it was withdrawn in 2014.

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TeslaCrypt was a ransomware trojan. It is now defunct, and its master key was released by the developers.

Linux.Encoder is considered to be the first ransomware Trojan targeting computers running Linux. There are additional variants of this Trojan that target other Unix and Unix-like systems. Discovered on November 5, 2015, by Dr. Web, this malware affected at least tens of Linux users.

<span class="mw-page-title-main">KeRanger</span> MacOS ransomware

KeRanger is a ransomware trojan horse targeting computers running macOS. Discovered on March 4, 2016, by Palo Alto Networks, it affected more than 7,000 Mac users.

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Ryuk is a type of ransomware known for targeting large, public-entity Microsoft Windows cybersystems. It typically encrypts data on an infected system, rendering the data inaccessible until a ransom is paid in untraceable bitcoin. Ryuk is believed to be used by two or more criminal groups, most likely Russian, who target organizations rather than individual consumers.

Royal is a cybercriminal ransomware organization known for its aggressive targeting, its high ransom demands, and its use of double extortion. Royal does not use affiliates.

References

  1. 1 2 Young, A.; Moti Yung (1996). "Cryptovirology: Extortion-based security threats and countermeasures". Proceedings 1996 IEEE Symposium on Security and Privacy. pp. 129–140. doi:10.1109/SECPRI.1996.502676. ISBN   0-8186-7417-2. S2CID   12179472. Archived from the original on 8 October 2022. Retrieved 8 October 2022.
  2. Larry Greenemeier (18 September 2013). "NSA Efforts to Evade Encryption Technology Damaged U.S. Cryptography Standard". Scientific American. Archived from the original on 18 August 2016. Retrieved 4 August 2016.
  3. "NIST Removes Cryptography Algorithm from Random Number Generator Recommendations". National Institute of Standards and Technology. 21 April 2014. Archived from the original on 29 August 2016. Retrieved 13 July 2017.
  4. 1 2 A. Young, M. Yung (2004). Malicious Cryptography: Exposing Cryptovirology. Wiley. ISBN   0-7645-4975-8.
  5. Korsakov, Alexey (2014). Cryptovirology and malicious software (PDF) (Master's thesis thesis). University of Eastern Finland, department of computer science.
  6. "FACT SHEET: Ransomware and HIPAA" (PDF). HHS. Archived (PDF) from the original on 13 April 2018. Retrieved 22 July 2016.
  7. SB-1137 that amends Section 523 of the Penal Code.
  8. "Tremor Description | F-Secure Labs". www.f-secure.com. Archived from the original on 24 June 2021. Retrieved 2 March 2021.
  9. "Sophos Security Labs: Real-Time Malware Threat Prevention". Archived from the original on 10 May 2008. Retrieved 23 May 2008.
  10. "Securelist". securelist.com. Archived from the original on 7 April 2015. Retrieved 2 March 2021.
  11. Young, Adam L. (2006). "Cryptoviral extortion using Microsoft's Crypto API". International Journal of Information Security. 5 (2): 67–76. doi:10.1007/s10207-006-0082-7. S2CID   12990192.