A social media expert told Congress on Tuesday that the Islamic State has over 45,000 Twitter accounts to attract followers from around the globe. 

Jihadist social media expert and Brookings Institution fellow JM Berger said the accounts consist of thousands of automated bots that use popular hashtags and celebrities to attract attention.

"Its highly organised social media campaign uses deceptive tactics and shows a sophisticated understanding of how such networks operate," Berger wrote in his report to the legislators. 

After the death video of journalist James Foley was spread across Twitter, the social network stepped up its methods of detecting and suspending accounts that promoted terrorism. 

A survey commissioned by Google Ideas and conducted by Berger and technologist Jonathon Morgan examined the types and number of accounts that have been suspended since fall 2014. 

They found that most of the thousands of suspended accounts tweeted three times more often than the average Twitter user, and received almost ten times as many retweets.

The complete results of the survey will be published by the Brookings Institution's Project on US Relations with the Islamic World in March. 

Nearly 18,000 IS-related accounts have been suspended since the fall, and Berger outlined three benefits to the current rate of suspension. 

"First, they reduce ISIS's reach among online populations at risk of radicalisation," he said. "Second, by allowing some ISIS accounts to continue with a lower profile, the current level of suspension activity preserves a substantial amount of open-source intelligence.

"Third, targeting the most active members of the ISIS supporter network undercuts ISIS's most important strategic advantage on platforms like Twitter – the 1,000 to 3,000 accounts that are, at any given time, far more active than ordinary Twitter users."

While new accounts are created to replace the suspended profiles, Berger said that the loss of momentum from the Twitter campaign suspensions has been "devastating."