Notorious computer security pioneer John McAfee has used a surprise appearance at a hacking conference to warn of threats against "freedom" thanks to privacy issues with technology.<p>Speaking at Def Con in Las Vegas, Mr McAfee called on hackers to "make a stand" against companies that seek highly personal information.<p>He blamed laziness for the spread of apps and websites that gleam information from users.<p>"We'd rather be safe, secure and comfortable than actually live," he said.<p>In 2012 Mr McAfee was accused of murdering his neighbour while living in Belize. He fled the country soon after and denies the charges.