Some 50,000 websites have been compromised as part of a sustained iframe injection attack campaign targeting vulnerable plug-ins for web servers and content management systems.
Attackers targeted holes in a string of plug-ins for blogging software — such as WordPress— including timthumb, uploadify and phpmyadmin.
When one was discovered, attackers would inject a malicious file and an iframe to link the compromised sites. Various browser-based attacks, including drive-by downloads, were also added.
At least 4000 new websites were infected each day, Sucuri malware researcher Daniel Cid told SC.
“So we believe that there are more than 50,000 sites compromised as part of this botnet,” Cid said.
“When all is said and done, you have a large network of compromised sites, all linking to each other and all with the same malware.”
He said a further 5000 were compromised today using the below malicious iframe.
Many of the queries probed for web hosting software Plesk, a finding backed by the Sans Internet Storms Centre that noted a sharp uptick in requests over port 8443, used by Plesk.
Vulnerabilities in WordPress plugins have been long understood. Last year, large malware campaigns including the LizaMoon attacks exploited those holes, while in November thousands of WordPress sites were hijacked through vulnerable instances of the TimThumb image resizer tool.