The Adobe updater periodically phones home and checks for software updates. The most recent Flash update also installs, by default, McAfee Security Scan Plus.
During the install you have the option not to install it but you have to select it manually.
McAfee Security Scan Plus isn’t good security software – it’s a marketing tool from MacAfee who want you to purchase their software, and should be considered AdWare.
I.T. Tips from fergus.it