Several websites using the FreeDNS hosting service from NameCheap have had visitors redirected to malicious, cloned sites via an IP address that once hosted command-and-control servers for the Conficker worm, cybersecurity firm Sucuri reported on Friday.

Sucuri's investigation into these DNS hijackings focused on a particularly suspicious NameCheap server whose domain was registered just days before by someone in Shanghai, China. This server pointed to an IP address that once served as part of the Conficker campaign but was repurposed to deliver ads, spam and malicious downloads via cloned websites.

“At this point it's not clear what happened. Either someone hacked into [individual] domain name registrar accounts and changed the name servers or someone compromised FreeDNS service and replaced one of their name servers,” Sucuri's blog post read. Sucuri reported that the malicious server was taken down and the affected name servers have returned to normal.