Companies around the world are reporting that they are affected by large-scale hacker attacks, the BBC reports. The British marketing agency WPP is just one of a dozen companies reporting problems.

A new type of ransomware

Ukrainian companies, including the main state electricity distributor and the main airport in Kiev, were among the first to report a Cyber-attack. Some experts believe that it could work again on ransomware, similar to the one used in the big attack last month, called "WannaCry." Computer expert Alan Woodward claimed that this seems to be a variant of ransomware that came out last year and was upgraded by criminals, and said its original name was "Petya." Petya is the type of ransomware that appeared early last year.

Criminals do not attack individual documents, but part of the computer system called the Master File Table (MFT). Such an attack is much faster and more efficient than targeting individual documents.

Earlier this year, a new and improved type of Petya called "Petrwrap" appeared. Although it can be detected by antivirus programs, once it starts spreading, it is very likely that lost documents will not be able to be recovered, Woodward warns. Experts advise users to update their security settings on their computers, and directions on how to do so can be found on Microsoft's site.

The biggest damage in Ukraine

Recorded Future Security Company spokesman Andrei Barysevich said that in the last 12 months he has encountered numerous malware that can be purchased online and costs just $ 28 in the forums.

He stressed that he thinks these attacks will not stop because the hackers consider them too inexpensive and said that the South Korean company has just paid $ 1 million to restore its data and this is a huge surplus for cyber criminals.

The attacks were also reported by the Central Bank of Ukraine, the airline company Antonov, and two postal companies.

The Russian oil company Rosneft and the Danish company Maersk also reported problems in their offices in the UK and Ireland. Spanish media reported that multinational companies such as Mondelez and DLA Piper were involved, while St Gobain's construction material was attacked in France. In Kiev, due to an attack, the computer system of the subway and several gas station stations also stopped working.

The attack also hit the radiation monitoring system at the Chernobyl power station, the world media reported. All the work was interrupted because the workers lost access to the system. A team of computer experts is currently working on solving the problem and the director of the shift told the Ukrainian newspaper, Pravda, that there is no threat from radiation.