Malware, short for malicious software, is a program designed to damage, disrupt or compromise a computer or device. More common names for malware are virus, ransomware, worms, trojans, spyware, etc. Malware is delivered to systems in a variety of ways, from links or attachments in a compromised email, to advertisements that entice you to click through to bogus websites that can appear legitimate.
One of the most common indicators of malware on a device is system slowness — slowness to open programs or browsers, slowness to log on and off your device, etc. Programs automatically opening and closing can also indicate that something malicious has been installed on your device. Another common indicator is unwanted programs being installed on your device. Random pop-ups and ads as well as toolbars appearing in your internet browser can all indicate compromise.