European Dropbox users have reported a sudden spike in spam received by email addresses associated with their accounts, raising fears that the service has suffered a security compromise.
Researchers have claimed skepticism around the existence of a spam botnet on Android devices, despite reports from Sophos and Microsoft claiming the issue was real.
Speculation surrounding the threat began last week when Terry Zink, a program manager for Microsoft Forefront Online Security, claimed spam messages were being sent using the Yahoo Mail app on Android devices.
Challenge-response techniques called "CAPTCHAs" designed to keep spambots off Web sites can easily be broken by humans who are paid to type in the responses, according to a new report from security firm Imperva.
CAPTCHAs, which stands for Completely Automated Public Turing test to tell Computers and Humans Apart, are created by programs and are intended to be difficult for computers to fill out.
Many of the LinkedIn e-mails alerts instructing users on how to reset passwords accessed by hackers were dumped into spam boxes, according to e-mail security vendor Cloudmark.
In a blog post last week, Andrew Conway, a Cloudmark researcher, said a substantial increase in spam reports last weekend were traced to LinkedIn password reset e-mail alerts
Yahoo said it will roll out globally this week a new antispam specification intended to make it easier for service providers to confidently discard suspicious email messages.
The specification, called DMARC (Domain-based Message Authentication, Reporting & Conformance), allows email senders to tell receiving services if they are using two other technologies to weed out spam.