The Islamic State was backed by 46,000 accounts on Twitter in 2014 :The Washington Post

This screen grab from an Islamic State group affiliated Twitter account, taken Sunday, Sept. 20, 2014, purports to show senior military commander Abu Wahib handing a flower to a child while visiting southern Iraq, as part of the group's broad social media campaign. (AP Photo, via Twitter)

The Islamic State, more than any extremist group before it, has become known for its social media savvy. In particular, the microblogging service Twitter has emerged as a tool for the group to spread propaganda extolling the virtues of life in its self-proclaimed Islamic caliphate and to warn its enemies.

Now, a new study from the Brookings Institution has investigated the group's practices on Twitter and come to the conclusion that there were at least 46,000 Islamic State-supporting Twitter accounts between September 2014 and December 2014  – and possibly as many as many as 90,000, though not all were active at the same time.

"The ISIS Twitter Census," written by J.M. Berger, a non-resident fellow at Brookings, and Johnathon Morgan, a technologist with CrisisNET, evaluated some 20,000 of these accounts to try to understand how they operated. They found that the typical Islamic State-tweeter was probably located in Syria or Iraq (though accounts were found as far away as Brazil) and that on average they had around 1,000 followers. Three-quarters had Arabic selected as their primary language, while almost one in five had selected English.

While most of these accounts bore no official relation to the governance of the Islamic State (many were presumably "ISIS fanboys," to use a derogatory term that has become common parlance), Berger and Morgan found at least 79 accounts that could be "official" when they looked in late December 2014. These accounts included Islamic State media outlets and well-known members.

The estimate 46,000 accounts may sound like a lot, but it's a drop in the ocean for a service like Twitter, which claims to currently have 288 million active users. Additionally, the Brookings study comes to the conclusion that many of the Islamic State-supporting accounts didn't have a big reach: While their average of 1,000 followers is higher than the average Twitter user, 73 percent of Islamic State-tweeters had fewer than 500 followers.

Only 4 percent had more than 5,000 followers and no overt Islamic State supporter had more than 50,000, though a few came close. Those are big numbers but nothing like the numbers we see in Western power users like President Obama (56 million) or Justin Bieber (61 million). The Brookings Institution itself has over 150,000 followers.

Despite the lack of followers, the Islamic State is able to make an impact on social media. Berger and Morgan put it down to tactics, particularly the work done by a small group  (between 500 and 2,000) of prolific users referred to as "mujtahidun" or "industrious ones" who tweet a large amount of content in short spaces of time. "This activity, more than any other, drives the success of ISIS’s efforts to promulgate its message on social media," the report notes. "Short, prolonged bursts of activity cause hashtags to trend, resulting in third-party aggregation and insertion of tweeted content into search results."

The report notes that 1,000 Islamic State supporting accounts were suspended by Twitter during the timeframe they examined (a Twitter representative told the New York Times that the figure was in fact significantly higher). This tactic appears to have accelerated recently, with reports at the start of March that Twitter had suspended 2,000 accounts in one week. Accounts linked to the Islamic State later threatened employees of Twitter with violence.

Berger and Morgan conclude that while the suspensions limit the success of the Islamic State in spreading its message on Twitter, they fail to completely wipe out propaganda efforts on the services. The study also warns of unintended consequences in the suspension campaign, most notably the isolation of pro-Islamic State accounts. Notably, some of the "official" Islamic State accounts had shifted to using accounts with high privacy settings and taking extra measure (including using Twitter's default 'egg' profile picture) to avoid detection.