We are skeptical about these products. They probably can't hurt, but don't let yourself get a false sense of security from using them.
If you want to block Java, the best way to do it is by setting your browser preferences to disable Java.
This is a complicated question with no simple answer, so we wrote a separate FAQ about it.
Generally, the latest version is the safest. Be sure to regularly check your browser vendor's Web pages for announcements of new versions. Look carefully - the announcements are not always prominent.
This is a general term for Java applets (programs) that exploit security bugs. There are some pages on the Web that demonstrate, with appropriate warning messages, some hostile applets. The applets we've seen are nuisance attacks rather than damaging attacks.