27 June 2017 could be called Ukrainian history’s “black cyber Tuesday”. On that day, the NotPetya (Petya.A, ExPetr) attack began, affecting almost all sectors in the country: communications, energy, banking, media, and transportation. The Petya ransomware is far from the first test of the strength of Ukraine’s infrastructure. Such attacks have been attempted at least three times. The first two attacks didn’t take place on such a large scale, but were highly unpleasant: in late 2015, the BlackEnergy virus, targeting energy company “Ukrenergo”, led to blackouts in some areas. Exactly a year later, in December 2016, some commercial banks and the Ministry of Finance were targeted along with, once again, Ukrenergo. But up to that point, nothing like this had happened. What it was Initially, Petya took the form of a file-encrypting virus which would subsequently demand a ransom. Hackers promised a decryption key to users who sent $300 worth of Bitcoins to their electronic wallet. However, these users received no code after transferring the funds, and decryption of the data remained impossible. Some experts, having analyzed the hackers’ strategy, noted that ransomware doesn’t work that way; receiving the ransom funds was not the goal of this attack’s organizers. As time passes, there is more and more support for the belief that the NotPetya malware was only disguised as ransomware. Its main purpose was another: the destruction of information stored on affected computers’ disks. Based on this, the malware can be categorized as a wiper, rather than ransomware. The encryption-decryption story was there only to divert users’ attention. There is also another version of the story. The alternate story argues that the attackers’ goal was to obtain control over all the infected computers, which would persist even after the removal of the virus and cleaning up of disks. In response to this, though, it can be observed that the method by which the attack was executed was too “loud”, attracting too much attention. A real spy would have attempted to gain a foothold, so to speak, on victims’ computers in the least noticeable way possible, without advertising the infection. Thus, an attempt to cause chaos in large organizations and companies, causing them material losses as well as damaging their image, seems more realistic. How it got in and spread One of the main infection vectors was the accounting software M.E.Doc, used for submission of reports and circulating electronic documents in a majority of Ukraine’s enterprises and organizations. An investigation carried out by Ukraine’s cybersecurity team showed that malicious code was injected into an update for the program. Thus, only the computers on which users downloaded the update were immediately infected. The malware then spread through corporate networks, including to machines on which the notorious M.E.Doc had not been installed. This was possible because back in the spring of 2017, the attackers gained control of an account used by an employee of the developer (Intellect Service), thereby receiving access to the program’s source code. An additional risk factor was the use of outdated software on the company’s server. That very server, in fact, went four years without being updated. Another way the file-encrypting virus arrived on computers was through phishing emails that contained links which triggered a download of the malware. After infection and a spontaneous reboot, access to these computers was blocked, and the files on their hard disks were encrypted. The virus damaged the master boot record, or MBR, leading to a complete inability to start the operating system. Who was affected, and how According to statistics, more than 70% of companies affected by NotPetya (Petya.A) are located in Ukraine. There were also infections reported in other countries:...