Many people continuously receive missed calls from unfamiliar numbers with familiar prefixes, but these calls only ring for a few seconds before hanging up. These may be missed calls from scammers to verify that the phone number is active, thereby serving spam advertising or fraudulent scenarios.

If the subscriber number is confirmed to be active, scammers may continue calling back from another number, impersonating banks, the Police, network operators, or familiar entities to build trust, then luring users into providing personal information, OTP codes, accessing links, or installing applications.

Note that one should not assume all calls from prefixes 022, 024, and 028 are fraudulent. These are legitimate landline area codes in Vietnam. What requires vigilance is unknown numbers calling unusually, even ringing once and hanging up, or answering the call with no signal on the other end of the line.

Bkav Cybersecurity experts recommend:

• Be cautious with missed calls from unfamiliar numbers; do not call back without verification.

• Do not provide personal information, bank accounts, passwords, or OTP codes over the phone.

• Do not access links, install applications, or follow instructions from callers of unknown identity.

• Proactively block and report phone numbers showing signs of harassment or suspicion.

• If the call is related to a bank, state agency, or service provider, proactively contact them via official channels for verification.

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