A similar intrusion at OPM last July was also linked to China, but no personal information was verifiably compromised. Still, facing a second breach within the span of a year raises real question about security practices within the agency. In this case, the intrusion was discovered by internal network monitoring systems, although it's still unclear whether the attackers exploited any residual effects from the earlier attack. "OPM has undertaken an aggressive effort to update our cybersecurity posture, adding numerous tools and capabilities to our networks," OPM's chief information officer told The Washington Post. "As a result of adding these tools, we were able to detect this intrusion into our networks."