OP POhjola customers faced a sixth day of disruption to their online banking services on Monday, as a deliberate denial of service (DDoS) attack continued. The attack especially affected OP customers trying to use the bank’s services from outside Finland.
Silja Nikkanen of OP said that the bank still had no information on who might be behind the problems. They began on New Year’s Eve and have now lasted six days. DDoS attacks involve individuals or groups sending huge amounts of traffic to overwhelm an online service, using more bandwidth than the organisation’s servers can handle.
They may use computers in different parts of the world which have been infected with viruses and are now controlled by the hackers. One common way to circumvent these attacks is to block traffic that may be suspicious, sometimes based on geographical location.
Nordea was also targeted by a DDoS attack, but the company’s services were back online quickly. OP, on the other hand, has struggled for days.
Timo Piironen of the National Bureau of Investigation (NBI) said on Monday that the technique used against OP was not particularly sophisticated. The operation could have been perpetrated, he said, by professional hackers or by enthusiastic amateurs.
On Monday Danske Bank’s online service was also down, but it was unclear whether this was also a DDoS attack or whether the outage was due to some other problem.