Twitter CEO Dick Costolo Getty / Steve Jennings Of Twitter's 284 million users, 24 million are just machines — apps or pieces of software — that ping Twitter's platform automatically "with no discernable user action involved," according to the company's disclosures to the SEC.

The fact that 8.5% of Twitter's "users" are not actually doing anything on the platform might be a problem. Business Insider has reported before that as many as 741 million people have opened a Twitter account and then abandoned it, and that a majority of Twitter users don't tweet in any given month. Twitter's stock price has been driven down to around $38 from a high of $55 in October last year in large part because its user growth hasn't been that strong, especially in comparison to Facebook.

Twitter doesn't see it that way of course. "These are real users who created Twitter accounts with real usernames and passwords, receiving Twitter content through third-party applications," a spokesperson tells us.

Twitter actually wants to build an ecosystem of people who plug their apps into Twitter. It makes Twitter more useful to everybody. And users who engage with Twitter via social media dashboards like Tweetdeck or Hootsuite are — in theory — heavier users of Twitter than those who tweet directly from the app.

In fact, 11.5% of all Twitter users connect to Twitter from third-party apps or software, the company says.

The Twitter spokesperson gave us this example: "HTC phones come with software called Blinkfeed that pulls social content from a variety of sources and presents it in one central spot via an app and widget. The user, though, first has to authenticate these services to pull from these feeds automatically."

But within that 11.5% are the 24 million — 8.5% — who, having connected, don't do anything except, at best, passively receive info.

Back in 2013, Twitter said that it expected the proportion of users it counted via apps that passively pinged the platform would decline over time. But the population of people who do "no discernable user action" on Twitter grew instead. Here's a chart, in millions, of their presence since Twitter first filed to go public, according to Twitter's SEC forms:

In Q2 2014, Twitter changed how it describes "monthly active users" (MAUs) who engage with Twitter via third-party apps. That's why there appears to be a sudden decline in inactive "active" users in that period. (Lara O'Reilly reported the change back in August.)

Previously, Twitter had defined that type of usage as coming from "mobile applications that automatically contact our servers for regular updates with no user action involved" (emphasis added). That language, however, understates the activity of users who use Twitter apps heavily. The new language gives two numbers: The MAUs coming from all third-party apps (11.5%); and within those, the users coming from third-party apps where Twitter cannot detect them actually doing anything (8.5%). The new language says those apps "may have automatically contacted our servers for regular updates without any discernable additional user-initiated action."

The chart above, therefore, shows the growth of users who, under Twitter's changing definition, may not have taken any action on the platform in a given month.

The chart goes some way to explaining the confusion among some observers as to why Twitter showed better-than-expected MAU growth in Q2 2014. At that time, Business Insider reported that some sources, who were trying to count users on Twitter via the application program interface (API) access the company gives to software developers, expected MAU growth to be soft. While those sources were not able to see directly the numbers that Twitter counts as MAUs, they derived an estimate of MAUs based on platform activity by users. In the event, Twitter had a breakout quarter and MAUs increased to 271 million, ahead of expectations. (Twitter then kicked out any developers who were publishing MAU estimates based on their API access.)

Some observers believed the World Cup — which was split across Q2 and Q3 — helped boost users. CEO Dick Costolo denied that was the case, arguing that the World Cup increased engagement but not MAU growth.

The changing definition of what a user is — and the fact that an "MAU" now includes accounts that connect passively to Twitter "without any discernable additional user-initiated action" — goes some way to explaining why those sources under-estimated Twitter's MAU growth. It's difficult to see users who aren't doing anything active on the platform.

This next chart shows Twitter's total reported MAUs (blue) in millions with MAUs minus those who didn't do any discernable action (red).

It indicates that in Q2, when Twitter gave analysts a positive surprise by recording 271 million users, only about 248 million of them did an overt action that Twitter could detect. That number is much closer to the 260 million MAUs Business Insider's sources predicted.

In Q3 2014, Twitter reported 284 million MAUS, of which only 260 million made an overt action that Twitter could detect.

Twitter reports its Q4 2014 numbers on Feb. 5. That report will update MAU growth and, crucially, analysts will be looking to see if Twitter can continue its MAU growth without the World Cup.

Disclosure: The author owns Twitter stock.