Because Spyware is designed to go undetected, it can be difficult to tell if you have Spyware installed on your devices. There are a couple of signs that you can look out for – Spyware has a tendency to slow machines down, since it is constantly transferring data to an attacker. And while your anti-virus should pick up on Spyware installations, if it’s out of date, or if the Spyware is new and anti-viruses have not picked up on it yet, there is a chance that it can pass by undetected.