Is it the Tamper Protection that is generating the message? If it is, you can safely disregard it. Norton has its own browser protection, and something in "Browser Protect" is coming into contact with one of Nortons keys. It is then blocked by Nortons self-protection, and this message appears. It is not a sign of malicious activity in itself, and if the "perpetrator" is a known safe program, you can regard it as more of an internal notification, and you don't have to do anything.
If the blocks happen so often that they interfere with something or cause slowdowns, the solution would unfortunately be to uninstall the offending program (or browser add-on in case). Otherwise, the only side-effect is a log filled with messages.
