Published: Nov 04, 2012 8:33 PM EST
Updated: Nov 05, 2012 7:31 AM EST

Several NBC websites were hacked on Sunday by a person or group calling itself "pyknic" and suggesting a possible link to the cyber-attack group Anonymous.

It appeared that the "defacement" of the affected sub-sites was cleaned up in a couple hours. NBC and its various websites appeared to be functioning normally as of Sunday evening Eastern time. However, older versions maintained by search engines such as Google or Bing still bore the message "hacked by pyknic" - a possible reference to an obscure hacker or "hacktivist" group.

The message said "Remember, remember the fifth of November." That reference suggested a link to Anonymous, a movement of cyber rebels.

However, conclusively determining responsibility for such attacks can be nearly impossible.

Also defaced Sunday was a Lady Gaga fansite, Gaga Daily.