In Reply to: Protect against/from posted by ESC on June 02, 2008 at 10:10:
: : What is the difference between protect against and protect from and in which context are these used?
: I can't answer that. But I've most often heard "guard against."
Damned prepositions again! ESC is quite right about "guard." Protect is not the same word as guard, but since it is often used to mean the same thing, its usage in this respect mostly coincides. The Oxford English Dictionary tries to find a rule (but not a rigid one) and has incorporated it into its first definition of "protect, verb transitive".
"To defend or guard from danger or injury; to support or assist against hostile or inimical action . . . Freq. with against, from. Also intr."
It's largely a question of style, but there are some situations in which "from" is the preferred choice, others in which "against" is preferred, and a large number in which you might go either way. I think one would have to make up a long list of particular cases to be sure of one's footing, but the OED provides a general rule. You protect someone or something from harm; you protect them against those things or persons that would cause the harm. For instance, you may wish to protect your throat from harm. To do so, according to a former well-known TV commercial, you must "guard against throat-scratch." Here, guard = protect, so you must protect your throat against causes of harm, like "throat-scratch," whatever that is. You must protect your child from harm. That may require protecting him or her against an abusive relative, or from defective toys. You must protect your left flank from being cut off by the enemy's cavalry.
If in doubt, I suspect that "from" is more inclusive and provides a safer choice. I don't know where to send you to be sure in any particular case.