Twitter on Monday trimmed the number of accounts that a user can follow in a single day in an effort to fight spam at the micro-blogging platform. The total number of accounts that can be added to a user’s list was cut to 400 from 1,000, the San Francisco-based internet firm said. “Follow, unfollow, follow, unfollow. Who does that? Spammers,” the Twitter safety team said in a tweet. “So we’re changing the number of accounts you can follow each day from 1,000 to 400. Don’t worry, you’ll be just fine.” Software programs referred to as “bots” sometimes run Twitter accounts, automatically following massive numbers of real people, a portion of whom tend to reciprocate by following back. High follower counts can then serve to raise the status of bot accounts, which can fire off website links or marketing content in tweets or messages to followers. Twitter policy bars use of the service for spreading spam, which it defines as “bulk or aggressive activity that attempts to manipulate or disrupt Twitter or the experience of users on Twitter to drive traffic or attention to unrelated accounts, products, services, or initiatives.” Factors taken into account by Twitter when determining if accounts are being used for spam is following and or unfollowing large numbers of accounts in short time periods.