a virus is keep edtting my htaccess

This virus, set back redcerits to a hostile website called “network-tease.ru” by editing my htaccess file. as a result google keeps marking down my website as “dangers”. I tried to deleted the file and renewed it, it workd for a while, but after few days the htaccess somehow was edited again by the virus.

I tried changing my FTP password, it did not help. I would greally appreciate any help.