In this paper, we study the experiences of practitioners in sectoral Computer Security Incident Response Teams (CSIRTs)—specialized teams that mediate between national cybersecurity authorities and the sector constituency. Through interviews with 18 professionals connected to the Informatiebeveiligingsdienst (IBD-CSIRT) for Dutch local governments, we uncover tensions in how key services are valued. For vulnerability notifications, while the CSIRT staff consider them a core service, many constituents hardly mention them, and systemic gaps in information forwarding mean that crucial alerts often never arrive. We extend these insights with 5 interviews across other sector CSIRTs and a validation workshop with 7 participants, all security officers from sector CSIRTs, revealing shared challenges in balancing technical expertise with sector knowledge, building trust-based relationships, and navigating institutional bottlenecks. Our findings contribute the first systematic account of how sector CSIRT professionals understand and perform their role, highlighting the tensions in providing sector-wide support to professionals with differing security needs.

Exposing intrusion campaigns has become a geopolitical tool, with governments and commercial firms publishing threat intelligence reports about hacking attempts and modus operandi. U.S. government officials have explained this as not just a defensive practice but also as a way to 'impose cost' on attackers by forcing them to develop new infrastructure, tools, and techniques. We empirically examine this claim by analyzing attacker behavior before and after publication of indicators of compromise (IOCs). Using IOC feeds from two leading commercial providers, we matched IOCs against a large dataset of real-world network traffic metadata. This enabled us to generate sightings retroactively, capturing malicious activity up to 150 days before and after publication. Unlike prior work focused on post-publication malicious activity, our method provides a more complete view over time. Our results show that most IOCs point to resources that attackers had already abandoned by publication, limiting their utility for detecting ongoing attacks and undermining the idea of 'imposing costs'. Statistical modeling further reveals that publication status has low explanatory power for sightings, suggesting that confounding variables exist. We also observed a 30-day delay between the peak of threat actor activity and IOC publication for one provider. This study is the first empirical assessment linking threat intelligence publication to attacker behavior, bridging computer science and international relations.