WASHINGTON—The Obama administration eased restrictions on selling smartphones, laptops and computer software to Iranians, part of an effort to thwart government crackdowns and censorship by spreading tools that help organize protests.

Text messaging, cellphone videos and social-networking sites all played a critical role in helping activists organize the Green Movement around Iran's 2009 elections.

While the protests were cast by some as a "Twitter Revolution," a brutal security crackdown prevented the demonstrations from evolving into an Arab Spring-type revolt that could topple the government.

The Treasury Department said on Thursday that it is lifting decades-old sanctions on a broad array of advanced communications equipment, from antivirus software and satellite phones to computer tablets and modems.

"There's been an increasing trend in their efforts in new and ever-more-complex and villainous ways to crack down on the free flow of information using sophisticated methods, and this is a response to their efforts," a senior administration official said.