Simply, Flash can also ride a wooden horse (repost)

When watching Flash animations on websites, receiving a "friend's" Flash greeting card, or even a QQ magic emoticon, one can easily get infected by a Trojan! Flash animation Trojans can be said to be omnipresent, with extremely wide-ranging attack power and coverage. Many friends must want to understand the principle behind Flash Trojans and wonder how attackers insert a Trojan into an SWF file. How should we guard against Flash Trojans?