Internet Porn

On a slightly off-topic but related issue - most of the internet porn solicitations I receive are "instant message" type spam. I get literally dozens of IMs every time I'm on-line (or my kids are...), of which it seems 95% are porn related (not a statistical sample - just my impression). "Stacey" and her friends are especially persistent. So far, my daughters regard it the same way I do - as harmless but extremely irritating. Nor have the indicated much interest in looking at the sites. However, I would like to know if there is any way to block IM's either in particular or in general? I'm a technically challenged old fart, so reprogramming something is simply not on. Curiously, I never had any such problem in Ukraine - one of the leading source countries for sexual trafficking in persons. Go figure...