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Main article: "CryptoLocker

Encrypting ransomware reappeared in September 2013 with a Trojan known as "CryptoLocker, which generated a 2048-bit RSA key pair and uploaded in turn to a command-and-control server, and used to encrypt files using a "whitelist of specific "file extensions. The malware threatened to delete the private key if a payment of "Bitcoin or a pre-paid cash voucher was not made within 3 days of the infection. Due to the extremely large key size it uses, analysts and those affected by the Trojan considered CryptoLocker extremely difficult to repair.[23][66][67][68] Even after the deadline passed, the private key could still be obtained using an online tool, but the price would increase to 10 BTC—which cost approximately US$2300 as of November 2013.[69][70]

CryptoLocker was isolated by the seizure of the "Gameover ZeuS "botnet as part of "Operation Tovar, as officially announced by the "U.S. Department of Justice on 2 June 2014. The Department of Justice also publicly issued an "indictment against the Russian hacker Evgeniy Bogachev for his alleged involvement in the botnet.[71][72] It was estimated that at least US$3 million was extorted with the malware before the shutdown.[10]

CryptoLocker.F and TorrentLocker[edit]

In September 2014, a wave of ransomware Trojans surfaced that first targeted users in "Australia, under the names CryptoWall and CryptoLocker (which is, as with CryptoLocker 2.0, unrelated to the original CryptoLocker). The Trojans spread via fraudulent e-mails claiming to be failed parcel delivery notices from "Australia Post; to evade detection by automatic e-mail scanners that follow all links on a page to scan for malware, this variant was designed to require users to visit a web page and enter a "CAPTCHA code before the payload is actually downloaded, preventing such automated processes from being able to scan the payload. "Symantec determined that these new variants, which it identified as CryptoLocker.F, were again, unrelated to the original CryptoLocker due to differences in their operation.[73][74] A notable victim of the Trojans was the "Australian Broadcasting Corporation; live programming on its television "news channel "ABC News 24 was disrupted for half an hour and shifted to "Melbourne studios due to a CryptoWall infection on computers at its "Sydney studio.[75][76][77]

Another Trojan in this wave, "TorrentLocker, initially contained a design flaw comparable to CryptoDefense; it used the same "keystream for every infected computer, making the encryption trivial to overcome. However, this flaw was later fixed.[35] By late-November 2014, it was estimated that over 9,000 users had been infected by TorrentLocker in Australia alone, trailing only Turkey with 11,700 infections.[78]


Another major ransomware Trojan targeting Windows, CryptoWall, first appeared in 2014. One strain of CryptoWall was distributed as part of a "malvertising campaign on the "Zedo ad network in late-September 2014 that targeted several major websites; the ads redirected to rogue websites that used browser plugin exploits to download the payload. A "Barracuda Networks researcher also noted that the payload was signed with a "digital signature in an effort to appear trustworthy to security software.[79] CryptoWall 3.0 used a payload written in "JavaScript as part of an email attachment, which downloads executables disguised as "JPG images. To further evade detection, the malware creates new instances of "explorer.exe and "svchost.exe to communicate with its servers. When encrypting files, the malware also deletes volume shadow copies, and installs spyware that steals passwords and "Bitcoin wallets.[80]

The FBI reported in June 2015 that nearly 1,000 victims had contacted the bureau's "Internet Crime Complaint Center to report CryptoWall infections, and estimated losses of at least $18 million.[11]

The most recent version, CryptoWall 4.0, enhanced its code to avoid antivirus detection, and encrypts not only the data in files but also the file names.[81]


Fusob is one of the major mobile ransomware families. Between April 2015 and March 2016, about 56 percent of accounted mobile ransomwares was Fusob.[82]

Like a typical mobile ransomware, it employs scare tactics to extort people to pay a ransom.[83] The program pretends to be an accusatory authority, demanding the victim to pay a fine from $100 to $200 "USD or otherwise face a fictitious charge. Rather surprisingly, Fusob suggests using iTunes gift cards for payment. Also, a timer clicking down on the screen adds to the users’ anxiety as well.

In order to infect devices, Fusob "masquerades as a pornographic video player. Thus, victims, thinking it is harmless, unwittingly download Fusob.[84]

When Fusob is installed, it first checks the language used in the device. If it uses Russian or certain Eastern European languages, Fusob does nothing. Otherwise, it proceeds on to lock the device and demand ransom. Among victims, about 40% of them are in Germany with the United Kingdom and the United States following with 14.5% and 11.4% respectively.

Fusob has lots in common with Small, which is another major family of mobile ransomware. They represented over 93% of mobile ransomwares between 2015 and 2016.


As with other forms of malware, security software might not detect a ransomware payload, or, especially in the case of encrypting payloads, only after encryption is under way or complete, particularly if a "new version unknown to the protective software is distributed.[85] If an attack is suspected or detected in its early stages, it takes some time for encryption to take place; immediate removal of the malware (a relatively simple process) before it has completed would stop further damage to data, without salvaging any already lost.[86][87]

Alternately, new categories of security software, specifically "deception technology, can detect ransomware without using a signature-based approach. "Deception technology utilizes fake SMB shares which surround real IT assets. These fake SMB data shares deceive ransomware, tie the ransomware up encrypting these false SMB data shares, alert and notify cyber security teams which can then shut down the attack and return the organization to normal operations. There are multiple vendors[88] that support this capability with multiple announcements in 2016.[89]

Security experts have suggested precautionary measures for dealing with ransomware. Using software or other security policies to block known payloads from launching will help to prevent infection, but will not protect against all attacks. Keeping "offline" backups of data stored in locations inaccessible to the infected computer, such as external storage drives, prevents them from being accessed by the ransomware, thus accelerating data restoration.[23][90]

There are a number of tools intended specifically to decrypt files locked by ransomware, although successful recovery may not be possible.[2][91] If the same encryption key is used for all files, decryption tools use files for which there are both uncorrupted backups ("plaintext in the jargon of "cryptanalysis) and encrypted copies; recovery of the key, if it is possible, may take several days.[92]

See also[edit]


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Further reading[edit]

External links[edit]

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