@zinia

Firefox that the malware is coming from. I'm also wondering why I would need to download and install something to clean the infection as suggested by essexboy - isn't Avast supposed to clean infections?
no security program have 100% detection and/or removal

removing malware can be a complex operation, the bad guiys use evry trick in the book to stay undetected or make it difficult to remove

if you need help, start your own topic and follow the logs to assist in cleaning malware guide at top in this forum section