Twitter's CFO is the only senior executive who has bought stock in 2015

There's a big trend in Twitter's SEC filings: Executives are selling stock. And it's not just a couple of them, there has been a long series of sales since the start of the year.

But there's one Twitter executive who's valiantly backing the company with his own money. Since the start of 2015, CFO Anthony Noto is the only Twitter executive who has bought stock in the company.

An SEC filing from Twitter dated August 4 shows that Noto bought 6,950 shares in Twitter. In today's market, those shares have a value of around $200,000 (£128,000). That brings Noto's total number of Twitter shares to 1,328,663, valued at around $36 million (£23 million).

What's significant here is that Noto is buying up Twitter stock when other insiders are selling their shares. Most of those sales are pre-scheduled, and designed to periodically reward executives for staying at Twitter with cash. They are not sales that indicate they are dumping Twitter.

But still. All of Twitter's top-ranking execs are able to buy Twitter stock whenever they want. And only Noto has done so.

Here's a look at the transactions in Twitter stock for the senior execs who are required to disclose trades to the SEC:

This isn't just a recent phenomenon. It's been going on since January.

Perhaps Noto is signalling to his colleagues that he's fully behind Twitter. Or perhaps he senses that Twitter's stock has been beaten down so far it looks like a good investment. As the CFO, he's got a pretty good view of what might happen in the future regarding Twitter's underlying business.

Morale inside Twitter is running low, sources have told Business Insider, due in part to the ongoing search for a CEO and a recent slump in its shares. An insider told us that some staff are considering leaving.

Noto is one of the people believed to be in the running for CEO of Twitter. Right now founder Jack Dorsey has stepped up and is managing the company on an interim basis, but Twitter's board wants a full-time executive (Dorsey is also CEO of payments company Square).