Verizon temporarily blocked traffic from some Web sites affiliated with the 4chan online forum on Monday after finding that some affiliate sites were apparently launching network attacks.
"Our network security system found traffic from some 4Chan Web sites that had strong potential to disrupt the Verizon Wireless network, affecting our customers' use of their services," Verizon spokesman Jeffrey Nelson wrote in an e-mail to CNET. "With continuing investigation, and ensuring no current risk of harm, we are giving the green-light to all 4Chan traffic. We will continue to monitor for any possibility of network harm."
He also posted an explanation on Twitter: "Never a block on 4Chan but some of its other sites were launching network attacks."
It was unclear which sites were affected and exactly what the trouble was. The sites appear to have been "explicitly blocked" for as long as three days, according to the 4chan status page.
, AT&T blocked a 4chan server after another site launched a denial-of-service type of attack called a SYN Flood attack on the site. 4chan users, notorious for their Internet pranks, responded angrily by on CNN's iReport citizen journalism site alleging that AT&T CEO Randall Stephenson had died.
Update 1:51 p.m. PST: Verizon posted this statement on the company's policy blog:
"Recently, Verizon Wireless security and external experts detected attacks from an IP address associated with the 4Chan family of web sites that was disruptive to our customers and our network. To protect both, we eliminated connectivity to the IP address. At no time was 4Chan itself blocked. Ongoing network security team monitoring has now determined there is no longer an immediate threat. Connectivity to those sites is being restored later today.
"Typically, these attacks involve someone sending hundreds of thousands of messages to wireless devices to round up active customer addresses for follow-up activity including hacker attacks. These 'sweeps' can jam our network and deliver unwanted electronic messages that also can drain customer devices' battery life and slow their operation.
"We take being the nation's most reliable wireless network seriously. Seriously enough to protect our customers and our network from malicious attacks, even if we get dinged in the blogosphere. It's easy to complain about 'blocking' when your wireless data connection is stable, fast and reliable. But try connecting to the web from your Droid or Blackberry when attacks slow - and potentially block - use of our network all together.
"We monitor against attacks and potential attacks to ensure the integrity of the Verizon Wireless network. Our customers expect nothing less."