Iranian government has maintained one of the world’s largest internet filters, blocking access to thousands of sites and IP addresses. Last week, the Islamic republic cut citizens’ access to Gmail and the secure version of Google Search. Iran has tightened cyber security since its uranium enrichment centrifuges were hit in 2010 by the Stuxnet computer worm, which Tehran believes was planted by arch-adversaries Israel or the U.S. Last month a commander in the elite Revolutionary Guard announced that Iran is ready to defend itself against any form of cyber war.
Source: https://thehackernews.com/2012/10/cyber-attack-on-irans-internet-system.html