Accusations that an Android-based botnet is spewing spam may, in fact, be no such thing, but instead a sign that criminals are exploiting bugs in the Yahoo Mail app for Google's mobile operating system, a security firm said today.
"There's no smoking gun, but my guess is that it's not malware," said Kevin Mahaffrey, co-founder and CTO of San Francisco-based Lookout Security, essentially dismissing the botnet possibility. "It's more likely an issue with the Yahoo Mail app."
Lookout has discovered what Mahaffrey called "potential security issues" in Yahoo's Android app, and reported its findings to the California search company's security team.
"They've acknowledged that they're looking into and working on these [issues], but until they complete their investigation, we are not disclosing any more information," Mahaffrey said in an interview Friday.
In a blog post Thursday, Lookout also said the vulnerabilities it found "have potentially broader implications for all Android users of Yahoo! Mail."
News first circulated Tuesday about a possible Android-based botnet - if accurate, a first - when Terry Zink, a program manager for Microsoft's enterprise-grade Forefront security product team, reported that spam messages were originating from Yahoo's servers and being sent from Android devices.
Google denies spam being sent by Android botnet
Other security researchers, including those at UK-based Sophos, reached the same conclusion after analysing some of the spam messages.
Google has denied that the spam is being sent by an Android botnet.
"Our analysis suggests that spammers are using infected computers and a fake mobile signature to try to bypass anti-spam mechanisms in the email platform they're using," Google told the IDG News Service yesterday.
Several security experts took Google's side, theorising that the spam actually originated from a run-of-the-mill botnet composed of compromised Windows PCs, and as Google said, had been disguised as mobile mail to avoid detection.
Mahaffrey and Lookout, however, offered a third explanation, that Yahoo Mail on Android contained vulnerabilities that spammers were exploiting.
"The potential security issues in Yahoo Mail for Android could have allowed the type of behavior that we, and others, have witnessed," said Mahaffrey, who again declined to go into specifics until Yahoo had investigated and if necessary, fixed its app.
More proof needed to determine the exact cause
The current version of Yahoo Mail for Android is 1.4.4, which was last updated 23 June, according to Google Play, the official Android app e-market.
Mahaffrey declined to comment when asked if Lookout's researchers had snooped through older versions of Yahoo Mail to find out if the "potential security issues" were introduced in v. 1.4.4, or had been present in earlier editions of the app.
"The jury is still out what this really is," said Mahaffrey. "There's been a lot of speculation and not a lot of proof, so we all need to take a step back and take a scientific approach to the problem. But unfortunately, the truth isn't always what gets the headlines."
Lookout continues to dig into the spam and Yahoo Mail for Android, said Mahaffrey, and the company will publish more information as it's available and in line with the concept of "reliable disclosure," a term used to describe keeping vulnerabilities secret until they're patched by the developer.
Yahoo did not reply to a request for confirmation of Mahaffrey's assertion that Yahoo Mail contained flaws that could have been used to spew spam from smartphones equipped with the app.