Businesses in Guernsey are being targeted by cyber attackers who demand a ransom to recover lost files, computer engineers have said.
Ten companies have been hit by attacks that lock a business out of its computer system until a ransom is paid.
No engineer has had any success in getting files back for customers so far.
One person has tried to pay the ransom, but the price went up from £400 to £1,000 in 24 hours.
“We would always urge any business that has been the subject of a cyber-attack to inform us,” detectives said.
“We have specialist officers who would investigate to attempt try and locate those responsible.”
Computer engineer Paul Domaille said the problems for one company began when they opened an email with the subject “remittance advice enclosed”.
He said: “I clicked on this email, the screen went black, clicked a few times and when I tried to look at quick books it was all gone.
“Everything stored on the computer was quickly encrypted. Messages then started to appear on screen asking for a ransom, in order to get the data back.
“The advice is not to pay it, go back to back up and that’s the only way to recover your files.”
Victims range from hotels and restaurants, to small businesses and individuals. In every case, there was a demand for money to unlock the computer.
Guernsey Police said: “We would always encourage businesses to have appropriate levels of cyber security and advise against clicking on emails from unknown sources.
“Additionally, we would advise businesses that regular reliable backing up of data, which is kept apart from their main system, would aid their rapid recovery from such an attack.”