Similar to the desktop software, web scripts are not spare from rampant piracy. A nullified script, also known as a nulled script is an illegal version of a script that has been pirated to remove security measures. Script developers and vendors usually include security checks like licensing, domain name validation or server callbacks to verify legitimacy of their products once sold. In the case of a nulled script, these security measures are removed and for most of the time replaced by other malicious codes.
Using a nulled script is foremost illegal and remember you will not be entitled for support, bug fixes and even upgrades. When downloading or purchasing script, always download from official or trusted sources.
If you’re a script developer, there is an online service called Nullwatch that provides real-time notification via email or phone whenever your script gets pirated and posted on the web.