“These systems were built primarily to detect known threats using signature-based approaches, which are insufficient against today’s sophisticated, constantly evolving attack techniques,” Young says. “Modern threats often employ subtle tactics that require advanced analytics, behavior-based detection, and proactive correlation across multiple data sources — capabilities that many legacy SIEMs lack.

In addition, legacy SIEM systems typically don’t support automated threat intelligence feeds, which are crucial for staying ahead of emerging threats, according to Young. “They also lack the ability to integrate with security orchestration, automation, and response tools, which help automate responses and streamline incident management.”

Without these modern features, legacy SIEMs often miss important warning signs of attacks and have trouble connecting different threat signals, making organizations more exposed to complex, multi-stage attacks.