A report of planted explosive devices in several Burgas schools emptied the classrooms yesterday.

Hundreds of children were evacuated.

All schools in the city were thoroughly checked for explosive devices.

Security expert Georgi Balev said that he does not define the case as a hacker attack, since no damage was done.

"We're seeing the sending of one mass message, which is where the whole problem comes from. It's quite easy to make an email and get it down in such a way that you don't know who the sender is. The email system was created in the 1970s and the way tracking doesn't help us much these days. You can't find out who sent the emails, it's very easy to create a server from where messages can be sent from anywhere in the world," he said.

And he adds that the author of the bomb threats is probably a depressed person, still a student.

Within 1-2 days it will be known if a child is behind the bomb threats in schools

"He wanted to feel stronger, for him the world is the school, that's why he sent emails to schools. He is probably from Burgas, because in his Telegram channel he uses Burgas media, which only Burgasians help. For me, this is a person who is in Bulgaria, in Burgas," said the expert. 

According to Plamen Petkov, one of the ways to find out who sent it is to use a virtual private network or VPN - which also masks the geolocation of the address from which it is sent.

"Through it, even if you are in Burgas, at the given moment it can show that you are in the Netherlands. Every email has an IP address that authenticates the identity. The purpose of the VPN is to change this identity so that it is not known who the person behind him," he explained.