Starting Wednesday evening we received numerous phone calls and also automatic alerts regarding Sophos antivirus detecting its own update as malware.
All the PCs running Sophos started throwing alerts generating false positives reporting SHH/Updater-B malware. We were getting slammed with alerts by email regarding the issue. In panic we called Sophos support but I guess we were not alone as every single Sophos customer was hit with this issue and their phone lines were hijacked with these customers. We could not get through to them.
Sophos later posted an apology and a knowledgebase article on how to resolve this problem which can be read here.