Police believe the arrest of 19 people on Tuesday may be just the first attack on an international computer crime gang that has stolen millions of pounds from British bank account holders.
Police officers from several police forces raided addresses in London to arrest 15 men and four women aged between 23 and 47 in connection with the theft of £6m.
They allegedly used the Zeus Trojan software to steal log-ins and personal banking details from computer users before drawing money from the accounts and sending it overseas.
Detective superintendent Charlie McMurdie, head of the Police E-Crime Unit (PeCU) told Computer Weekly that the investigation was continuing, along with several other "nationally significant" cases. She said they were likely to raise estimates of the stolen money "considerably".
She said detectives and investigators from the financial services sectors were still checking computers confiscated in the dawn raid for further intelligence. She was also working with international law enforcement agencies to follow up leads.
She said the gang had hit "thousands" of victims, but the amounts stolen had been small "to keep them under the radar".
"The banks compensated the victims, but this is not a victimless crime," McMurdie said. "The UK economy pays because the banks' insurance premiums go up and the banks reduce the interest they could otherwise pay savers to pay the higher premiums."
McMurdie renewed her call for citizens to be careful of what personal data they put online, what e-mails they opened, and to ensure that their anti-malware programs were up-to-date and switched on at all times.
McMurdie said the PeCU, which has been running formally for about two years, had arrested at least 70 people so far in connection with computer-enabled crimes worth millions to criminals.
She said the past two years had seen the establishment of good working relationships with foreign counterparts and finance industry investigators.
Investigations, especially when they led overseas, were complex and difficult and could take 12 to 18 months to conclude, she said. Those found guilty had been jailed for an average of 4.5 years, McMurdie said.
The PeCU had a difficult birth, made painful by a shortage of money. "We keep on arresting people, trying to show good results to keep the money flowing," McMurdie said.
She said the use of information technology to commit crime was rising. "The availability of tools that even novice (criminals) can use is increasing. This is something we have to take seriously," she said.