(Simon Dawson/Bloomberg)

Social media is as mighty as the sword — and wielding it on behalf of America's enemies can land you behind bars.

A U.S. district judge sentenced a Virginia teen to more than a decade in prison Friday after he used Twitter to help ISIS supporters hide their financial transactions and would-be foreign fighters looking to travel to Syria.

Ali Shukri Amin won't just have to serve a 136-month sentence after pleading guilty to giving "material support" to ISIS — he'll also have to let the government monitor his Internet usage for the rest of his life. But the sentence is actually somewhat lighter than what prosecutors had sought, which was 15 years in prison.

With a now-suspended Twitter account, @Amreekiwitness, that at one point had over 4,000 followers and 7,000 tweets, the 17-year-old allegedly helped explain to ISIS supporters how to use Bitcoin, the anonymous virtual currency, to cover their financial tracks. Amin also helped arrange travel to Syria for a would-be foreign fighter from Prince William County, Va.

Court documents show that Amin regretted the decision to help the Islamic State.

"I became lost and caught up in something that takes the greatest and most profound teachings of Islam and turns them into justifications for violence and death," he wrote in a letter to the judge. Amin, a former student at Osbourn Park High School in Manassas, Va., pleaded guilty in June.

"Those who use social media as a tool to provide support and resources to ISIL will be identified and prosecuted with no less vigilance than those who travel to take up arms with ISIL,” said U.S. Attorney Dana Boente in a Justice Department statement.

Social media platforms have enabled ordinary people to organize and communicate like never before. But Friday's sentencing is a reminder that technology is also blurring the lines between speech and action — and you never know who might wind up seeing what you post.