VoIP Number Recycling Helps Scammers Bypass Reputation Filters

Researchers (Cisco Talos) report an increase in telephone-oriented phishing and scam campaigns that embed VoIP numbers in malicious emails. Attackers favor programmable Communications Platform-as-a-Service providers to rapidly provision large, sequential blocks of E.164 numbers, use Direct Inward Dialing blocks and automated provisioning to scale, and rotate/recycle numbers (median malicious-number lifespan ~14 days, typical active use 2–6 days) to evade reputation-based filters; the same numbers are often reused across different lures and business contexts.