Social media platforms use a mix of automated systems, artificial intelligence, and human moderation to detect when accounts are being bought and sold. Here’s how they do it:

1. Unusual Login Activity

• Platforms track IP addresses, device fingerprints, and geolocation data.
• If an account suddenly logs in from a new country or multiple locations in a short period, it raises a red flag.

2. Sudden Changes in Behavior

• If an account that previously posted personal content suddenly starts posting ads, promotions, or spam, it gets flagged.
• A sharp increase in follower count, especially from low-quality or bot accounts, is another indicator.

3. Inconsistent Engagement Patterns

• Platforms analyze engagement history—if an account’s likes, comments, and shares drastically change overnight, it can signal account flipping.
• Fake followers and engagement from click farms leave digital footprints.

4. Mass Account Creation and Similarities

• Platforms monitor bulk account creation from the same IP address, using similar usernames, email domains, or device IDs.
• Bots running these operations often leave detectable patterns.

5. Violation of Terms of Service

• Many platforms prohibit the buying and selling of accounts. If they detect an attempt through flagged keywords in messages or external marketplaces, they may intervene.

6. Reports from Users

• Users sometimes report suspicious accounts, prompting manual reviews.

7. Payment and Transaction Tracing

• Some platforms track transactions that indicate account sales, such as money transfers between known account-selling sites and social media users.

8. AI and Machine Learning Models

• Advanced algorithms analyze behavioral patterns, helping platforms identify and take down suspicious accounts.

When accounts are suspected of being sold or transferred, platforms may shadowban, temporarily lock, or permanently suspend them. In some cases, they require identity verification before allowing access again.