New Banking Trojan Horses Gain Polish

Criminals today can hijack active online banking sessions, and new Trojan horses can fake the account balance to prevent victims from seeing that they're being defrauded.

By Robert Vamosi

November 24, 2009 — PC World —

Criminals today can hijack active online banking sessions, and new Trojan horses can fake the account balance to prevent victims from seeing that they're being defrauded.

Traditionally, such malware stole usernames and passwords for specific banks; but the criminal had to access the compromised account manually to withdraw funds. To stop those attacks, financial services developed authentication methods such as device ID, geolocation, and challenging questions.

Unfortunately, criminals facing those obstacles have gotten smarter, too. One Trojan horse, URLzone, is so advanced that security vendor Finjan sees it as a next-generation program.

Greater Sophistication

Banking attacks today are much stealthier and occur in real time. Unlike keyloggers, which merely re­­cord your keystrokes, URLzone lets crooks log in, supply the required authentication, and hijack the session by spoofing the bank pages. The assaults are known as man-in-the-middle attacks because the victim and the attacker access the account at the same time, and a victim may not even notice anything out of the ordinary with their account.

According to Finjan, a so­­phisticated URLzone process lets criminals preset the percentage to take from a victim's bank account; that way, the ac­­tivity won't trip a financial institution's built-in fraud alerts. Last August, Finjan documented a URLzone-based theft of $17,500 per day over 22 days from several German bank ac­­count holders, many of whom had no idea it was happening.

But URLzone goes a step further than most bank botnets or Trojan horses, the RSA antifraud team says. Criminals using bank Trojan horses typically grab the money and transfer it from a victim's account to various "mules"--people who take a cut for themselves and transfer the rest of the money overseas, often in the form of goods shipped to foreign addresses.

URLzone also seems to detect when it is being watched: When the researchers at RSA tried to document how URLzone works, the malware transferred money to fake mules (often legitimate parties), thus thwarting the investigation.

Silentbanker and Zeus

Silentbanker, which appeared three years ago, was one of the first malware programs to em­­ploy a phishing site. When victims visited the crooks' fake banking site, Silentbanker in­­stalled malware on their PCs without triggering any alarm. Silentbanker also took screenshots of bank accounts, redirected users from legitimate sites, and altered HTML pages.

Zeus (also known as Prg Banking Trojan and Zbot) is a banking botnet that targets commercial banking accounts. According to security vendor SecureWorks, Zeus often focuses on a specific bank. It was one of the first banking Trojan horses to defeat authentication processes by waiting until after a victim had logged in to an account successfully. It then impersonates the bank and unobtrusively injects a request for a Social Security number or other personal information.

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