Most of us can't resist #free things, but we need to realise the difference between getting a free ballpoint pen and a USB stick.
With the pen, the worst thing it can happen is it running out of ink too soon; with the USB stick however, there is enough #space for it to be filled with viruses that can breach your computer's firewall the instant it is plugged in, and then do enough damage to render a computer useless, whilst copying all of your data to an unknown cloud!
Residents of Pakenham, a suburb of Melbourne (Australia) have found unmarked USB sticks in their letter boxes. Unfortunately, most couldn't resist plugging them in to their computer only to find out that they were filled with malware. The local Police had to issue a public warning against the use of these free USB sticks.
It is not uncommon for USB sticks to be used to carry and transmit viruses to computers. Stuxnet, one of the most sophisticated known pieces of malware, used to attack Iranian nuclear centrifuges was very likely carried on an infected USB stick.
Although some users become distrustful when #software asks them to download something, apparently innocent Word files can be harmful too.
Bear in mind:
Never use unknown USB sticks;
When you have doubts about a file someone unexpectedly sent to you, don't open it without first contacting the person who supposedly sent it.