Try to keep your computer in a safe location. Hardware alterations are more likely on public computers, in internet cafés or libraries, and on desktop computers, where a device is easier to hide.
Other hardware alterations are much more complicated and expensive to install. For an example, see <a href="https://arstechnica.com/tech-policy/2014/05/photos-of-an-nsa-upgrade-factory-show-cisco-router-getting-implant/">Ars Technica: Photos of an NSA “upgrade” factory show Cisco router getting implant</a>.
