Sophisticated phishing attacks launched against Outlook Web App users

A cyberespionage group has been using advanced spear-phishing techniques to steal email log-in credentials from the employees of military agencies, embassies, defense contractors and international media outlets that use Office 365’s Outlook Web App.

The group behind the attack campaign has been operating since at least 2007 according to researchers from Trend Micro, who published a research paper on Wednesday about the attacks they dubbed Operation Pawn Storm.

The Pawn Storm attackers have used a variety of techniques over the years to compromise their targets, including spear-phishing emails with malicious Microsoft Office attachments that installed a backdoor-type malware program called SEDNIT or Sofacy, or selective exploits injected into compromised legitimate websites.

The group used one particularly interesting technique in email phishing attacks against organizations that use the Outlook Web App (OWA), which is part of Microsoft’s Office 365 service.

For each phishing attack, the group created two fake domains: one very similar to that of a third-party website known to the victims—like that of an upcoming industry conference for example—and one similar to the domain used by the targeted organization’s Outlook Web App deployment.

The attackers then crafted phishing emails with a link to the fake third-party site where they hosted non-malicious JavaScript code whose purpose was twofold: to open the actual legitimate site in a new tab and to redirect the already opened Outlook Web App browser tab to a phishing page.

“The JavaScript made it appear that the victims’ OWA sessions ended while at the same time, tricked them into reentering their credentials,” the Trend Micro researchers wrote in their paper. “To do this, the attackers redirected victims to fake OWA log-in pages by setting their browsers’ open windows property.”

This technique does not exploit any vulnerabilities and works in any popular browser, including Internet Explorer, Mozilla Firefox, Google Chrome and Apple’s Safari, the researchers said. However, two conditions need to be met: the victims need to use OWA and they need to click on the embedded links from OWA’s preview pane, they said.

This can be a powerful attack, because the victims know they had a legitimate OWA session opened in that browser tab and might not check if the URL has changed before re-entering their credentials.

In addition to using domain names that were very similar to those used by the targeted organizations for their real OWA log-in pages, in some cases the attackers even purchased legitimate SSL certificates so that the victims’ browsers display the HTTPS secure connection indicators for the phishing sites, the Trend Micro researchers said.

Among those targeted with this technique were employees of the U.S. private military company ACADEMI, formerly known as Blackwater; the Organization for Security and Co-operation in Europe (OSCE); the U.S. Department of State; U.S. government contractor SAIC; a multinational company based in Germany; the Vatican Embassy in Iraq; broadcasting companies in several countries; the defense ministries of France and Hungary, Pakistani military officials; Polish government employees, and military attachés from various countries.

The phishing baits used by the attackers included well-known events and conferences that their victims were interested in.

“Apart from effective phishing tactics, the threat actors used a combination of proven targeted attack staples to compromise systems and get in to target networks—exploits and data-stealing malware,” the Trend Micro researchers said. “SEDNIT variants particularly proved useful, as these allowed the threat actors to steal all manners of sensitive information from the victims’ computers while effectively evading detection.”