In their April Online Fraud Report RSA reports on the activity of online fraudsters, full summary below.

As well as the usual interesting statistics on fraudulent activity this report sheds light on the changes to the Citadel Trojan.

Citadel Trojan hooks system processes to isolate bots from AV and security.

The Citadel Trojan was first introduced for sale to cybercriminals in the Russian-speaking underground in February 2012. The Trojan, which was initially based on the Zeus Trojan’s exposed source code, is already at its second upgrade release, version 1.3.3.0, which was shared with its customer-base on March 15th.

One of the features included in the initial report and communicated by Citadel’s developers in late February related to a Trojan feature they have apparently implemented: DNS Redirection. Per the feature list, the developer claimed that unlike other Trojans, Citadel does not modify the “Hosts” file on the infected PC (all too often used for local Pharming), but rather allows the botmaster to block or redirect any URL they wish to prevent the bot from reaching.

To add value for their customers, the developers went the extra mile to add a list of AV software providers and security scans to the DNS redirection lists embedded into the configuration. On a change-log posting from the team, the developer specified that at least 104 different security-vendor URLs were added to this feature.

RSA researchers were able to confirm that the DNS-redirection method embedded into the Citadel configuration file was not a feature available in the original Zeus Trojan; it is new programming, courtesy of the Citadel team.

The Citadel Trojan’s configuration contained more than 650 different URLs of a large variety of AV-providers and security scanning services based out of different countries (USA, DE, RU and more). Each ‘forbidden’ URL was followed by a “=” mark and the IP mask address to which the botmaster wants the victim rerouted.

Another interesting feature analyzed by RSA researchers appeared in a Citadel variant, raising questions as to redirection scheme to Citadel resources. At first sight, the analysis result seemed somewhat peculiar, showing that Citadel was using legitimate URLs as its C&C’s drop point as well as the configuration update point (Google, CNET).

Phishing Attacks per Month

After a brief peak in phishing that came in the beginning of the year, the two months which followed have shown a slight decrease. February marked a 30% drop in worldwide phishing volume and March followed with another 9% drop with 19,141 unique phishing attacks identified by RSA in March. When compared year over year, March 2012 saw a 9% increase from the phishing volume in March 2011.

Number of Brands Attacked

The number of brands targeted through March increased 8% compared to February, standing at a total of 303 brands targeted by phishing attacks.

US Bank Types Attacked

There was a considerable increase in the phishing volume experienced by U.S. regional banks last month – increasing from just 7% in February to 30% in March. Meanwhile, attacks against U.S. nationwide banks decreased 24%. This isn’t surprising as phishers tend to alternate their cashout schemes by aiming at the small and regional institutions as well.

Top Countries by Attack Volume

The most prominent change in March in attack volume was the 23% increase for the UK and a 24% decrease for Canada. Overall, the countries that are consistently targeted most by phishing attacks include the U.S., UK, Brazil, Canada, the Netherlands and South Africa.

Top Countries by Attacked Brands

In March, about three out of ten attacks were targeted at brands in the U.S and one out of ten targeted at brands in the UK. This is not surprising as these two countries also continue to see the most volume of phishing attacks overall.

Top Hosting Countries

The U.S. hosted just slightly over half of the phishing attacks identified in March. 8% of attacks were hosted in Brazil, showing a 5% increase from February. Sixty other countries were responsible for hosting 17% of phishing volume in March.

Previous RSA Online Fraud Report Summaries:

  • The RSA March 2012 Online Fraud Report Summary here.
  • The RSA February 2012 Online Fraud Report Summary here.
  • The RSA January 2012 Online Fraud Report Summary is here.
  • The RSA December 2011 Online Fraud Report Summary is here.
  • The RSA November 2011 Online Fraud Report Summary is here.
  • The RSA October 2011 Online Fraud Report Summary is here.
  • The RSA September 2011 Online Fraud Report Summary is here.

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