Sophos Uncovers Mass Link Spam In Google’s Search Results Via Cloaked PDFs
Hackers use PDF documents to inject links and keywords and -- through cloaking techniques -- scam searchers to go to other web sites. Sophos, an IT security company, has uncovered a case of Google search spam involving “hundreds of thousands” of cloaked PDF documents with links that redirect human users to suspicious websites. It’s similar to the long-running type of hacking/spamming that involves placing HTML-based web pages on hacked websites, but in this case involves placing PDFs. The technique may not be necessarily new, but Sophos documented cases where the PDF content is ranking highly in Google’s search results. The company informed Google about this technique, but decided to publish their findings after not hearing back from Google. We also reached out to Google early this morning and have not heard back. Sophos said they think this technique works because “Google implicitly trusts PDFs more than HTML.” Honestly, we are not so sure how true that stat...