A joint alert (PDF) issued by the FBI, the Financial Services Information Sharing and Analysis Center (FS-ISAC), and the Internet Crime Complaint Center (IC3) states that criminals are using spam and phishing e-mails, keystroke loggers, and Remote Access Trojans (RAT) to compromise financial institution networks and obtain employee login credentials.
"The stolen credentials [are] used to initiate unauthorized wire transfers overseas," the alert states. "The wire transfer amounts have varied between $400,000 and $900,000, and, in at least one case, the actor(s) raised the wire transfer limit on the customer's account to allow for a larger transfer. In most of the identified wire transfer failures, the actor(s) were only unsuccessful because they entered the intended account information incorrectly."
The cybercriminals primarily used spam and phishing emails to target their victims, the alert states. Once compromised, keyloggers and RATs installed on the financial institution employees' computers provided the the criminals with "complete access" to internal networks and logins to third-party systems, it says.
Variants of Zeus malware were also used to steal employee credentials in a few reported incidents.
In some instances, the criminals stole multiple employee credentials or administrative credentials to third-party services and were able to circumvent authentication methods used by the financial institution, the report states. "This allowed the intruders to handle all aspects of a wire transaction, including the approval," it says.
"The unauthorized transactions were preceded by unauthorized logins that occurred outside of normal business hours using the stolen financial institution employees' credentials," the alert states. "These logins allowed the [criminals] to obtain account transaction history, modify or learn institution specific wire transfer settings, and read manuals providing information and training on the use of US payments systems."
Small to midsize banks or credit unions have been targeted in most of the reported incidents, but a few large banks have also been affected, the report says.
In some of the incidents, before and after unauthorized transactions occurred, the bank or credit union suffered a distributed denial-of-service (DDoS) attack against its public website or Internet Banking URL.
"The DDoS attacks were likely used as a distraction for bank personnel, to prevent them from immediately identifying a fraudulent transaction, which in most cases is necessary to stop the wire transfer," the alert says. Some of the attacks used Dirtjumper, a commercial crimeware kit that can be bought and sold on criminal forums for approximately $200.
Have a comment on this story? Please click "Add a Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.