Ricardo Kawase and colleagues at the University of Hanover in Germany created FireMe! as a way of reminding everyone how risky it can be to complain about your job publicly on Twitter.
They found almost 22,000 people who had tweeted about their job or boss in a negative way in a single week last June.
The team used an algorithm that looked for telltale phrases indicating someone had tweeted something negative about their boss or job, New Scientist reported.
Each alert also contained a link which, if followed, gave them their FireMeter! score - their chance of being fired as a percentage.
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It was calculated on the basis of how often they had mentioned their job negatively in the past 100 tweets and how often they swore.
Out of a total of 4304 FireMe! alerts sent in the space of three weeks, 249 recipients had deleted the tweet when it was checked two hours later.
An analysis found that people who tweeted negatively about their job generally tweeted more than regular users and had fewer followers than those who tweet positive things about their workplace.
The team said that young or inexperienced users would certainly benefit from post-hoc privacy alerts and warnings like FireMe!
"Potential dangers of personal, negatively loaded tweets remain abstract for most users, until the damage has been done," they said.