The technicians worked on Bangladesh's Real-time Gross Settlement (RTGS) system, used to transfer money among Bangladeshi banks, three months before hackers attempted to steal US$951 million from the central bank. The work opened up "a lot of loopholes" in bank computer systems, said the head of the criminal investigation department leading the investigation.
Bangladeshi police want to interview the SWIFT technicians to find out whether their actions were intentional or negligent, Mohammad Shah Alam told Reuters.
Police and bank officials told the news agency that a number of actions last October left the bank more vulnerable after the RTGS system was set up and connected to the SWIFT network, which provides messaging services to around 11,000 financial institutions worldwide.
SWIFT staff declined to speak to Reuters about the allegations, and did not immediately respond to requests from IDG News Service for comment.
The technicians did not follow usual security procedures, Bangladeshi bank and police officials told Reuters, leaving the bank's SWIFT messaging system remotely accessible, protected only via a simple password and no firewall.
Instead of building an isolated network for the RTGS system and linking that to the SWIFT network, the technicians connected both systems to a network linking 5,000 central bank computers to the open Internet, police officials told the news agency.
In addition, no firewall was placed between the RTGS and SWIFT networks to prevent the exchange of malicious traffic, and the switch used to connect the networks was not a modern, managed model but an old, unused one found at the bank, the agency reported.
The room containing SWIFT networking equipment at the bank was kept locked for security reasons, but the technicians installed a wireless connection, making it accessible from other offices there, securing it with only a simple password and leaving it connected after they left, the officials said.
Finally, a computer was connected to the SWIFT systems without following the usual procedure of disabling its USB port, making it possible for malware to be introduced from a thumb drive, police told the agency.
That port was still accessible when the theft was discovered in February, said the report, citing a bank official.
Hackers appear to have installed custom malware to interfere with the SWIFT messaging system.
During the theft, fraudulent SWIFT messages were sent to the U.S. Federal Reserve Bank in New York seeking to transfer $951 million from Bangladesh Bank's account there to accounts elsewhere. Most of those transfers failed but around $81 million was sent to a bank in the Philippines, much of which remains unrecovered.