More than 15 percent of Mitt Romney's Twitter followers may be generated by paid services that use fake accounts to artificially inflate the number of people subscribed to the presumptive Republican nominee for US president, according to a new report.

The report comes from researchers at security firm Barracuda Labs, and it cites the addition last month of 116,922 followers to @MittRomney in a span of just 24 hours. The infusion on July 21 represented a 17-percent spike in accounts following Romney. A quarter of those new accounts were less than four days old, and 23 percent of them had never issued a single tweet. Ten percent have since been suspended by Twitter for unspecified reasons.

"Based on the above distinguishable features, we believe most of these recent followers of Romney are not from a general Twitter population but most likely from a paid Twitter follower service," Barracuda Labs Research Scientist Jason Ding wrote in the report. Such services allow customers to buy followers for any Twitter account, he stressed, so it's not clear if the fakes were purchased by Romney, his supporters, or his political foes.

At the time of this writing, Romney's account had 782,476 followers.

Twitter follower services—which on average charge $18 for 1,000 followers—are part of a thriving underground market, Ding said. A dealer with 20,000 fake accounts at her disposal can earn as much as $800 per day for seven weeks. Dealers can also charge extra for selling tweets or retweets. Using the first 100 returns from this Google search, Ding counted 20 eBay sellers and 58 websites that marketed Twitter following services. A single dealer may control as many as 150,000 accounts.

Ding identified more than 11,000 "abusers," which he defined as those accounts that were followed by the fake Twitter users. On average, each abuser had 48,885 followers. Three-fourths of the abuser accounts included a URL associated with it, compared to 31 percent for random Twitter users. The above-average number suggests abusers "might buy followers for website promotional purposes," Ding said.

The creation of fake accounts is a violation of Twitter's terms of services, but the microblog officials show few signs of enforcing such prohibitions. Witness the account belonging to @kashifrox, for instance. It boasted 607,522 followers at publication time, and the claim: "i can add up to 100k to 150k followers to youy [sic] twitter account."

Ars has reached out to Romney officials for comment on Ding's report. This post will be updated if they respond.