What Asus router have you got ? Considering going down this route as the Homehub 5 is somewhat short of configuration options. Preferably something that can be flashed with ddwrt if the stock rom isn't configrable enough.
Two strategies: Prevention and Recovery.
Prevention is good AV software (AVG or Avast are fine), not clicking dodgy links or installing software with unknown provenance.
Recovery is having a backup strategy; get a USB hard drive (preferably two, keeping one off site) and copy all your valued...