Facebook scans the contents of messages that people send each other on its Messenger app, blocking any content that contravenes its rules, it has emerged.
The scandal-hit firm, still reeling from the Cambridge Analytica debacle, checks images and links for illegal or extreme content using automated systems.
What you write in your messages may also be read manually if it’s flagged to moderators for breaching Facebook’s community guidelines.
While the intentions behind the practice may be well-meaning, the news is likely to add to users’ concerns over what the social network knows about them.
It follows revelations that the Trump-affiliated consulting firm obtained data on at least 50 million unsuspecting Facebook users.
This information was used to target voters in the US, based on psychological profiling, with political adverts spreading disinformation.
Facebook is also facing criticism for collecting years of data on call and text histories from Android users.
CEO Mark Zuckerberg confirmed the policy during a podcast interview with Vox’s editor at large, Ezra Klein.
Zuckerberg told his host a story about receiving a phone call from staff at his Mountain View firm.
He was informed that their systems had blocked attempts to send inflammatory Messenger instant messages about ethnic cleansing in Myanmar.
About the experience, the 33-year-old billionaire said: ‘In that case, our systems detect what’s going on.
‘We stop those messages from going through.’
The news has been met with mixed reactions on social media, with a number of users expressing concern.
Messenger says that it doesn’t use data from messages it has scanned for the purposes of advertising, according to reports in Bloomberg.
The company told the website that it uses the same tools to prevent abuse in messages that are in place across Facebook as a whole.
Users are also able to flag posts or messages that they feel are in violation of the site’s house rules.
This will either cause one of the social network’s community operations team to manually review the content, or automated systems can also make decisions.
‘Keeping your messages private is the priority for us,’ a Facebook Messenger spokesman said in a statement to MailOnline.
‘We protect the community with automated systems that detect things like known images of child exploitation and malware. This is not done by humans.
‘We do not listen to your voice and video calls.’
But that is likely to be of little comfort in the current climate, with privacy at the forefront of many Facebook user’s minds.
One Twitter user, Kevin Chastain, claims to have experienced Messenger texts being used to target advertising, tweeting: ‘So I was messaging my wife about dinner tonight mentioned a particular place on Facebook messenger and then opened up Facebook about to see an ad for that restaurant.
‘Tell me they aren’t in on every convo I have. Scary!’