This case originates from the security lead of a large enterprise’s customer service center. The center handles customer service operations for multiple business lines within the group, with daily service volume exceeding 100,000 interactions. Equipped with a comprehensive information security protection system including SIEM, EDR, and multi-layered security facilities, this seemingly robust defense system revealed significant flaws during a supply chain attack incident in late 2023.
This document records the in-depth reflections and practical experiences of this security lead during the incident response. Although the event was ultimately controlled in time without major losses, the exposed issues are universal and worthy of industry reference.
Incident Overview
In December 2023, the security team discovered a supply chain attack targeting customer service information systems. Attackers infiltrated the internal network by compromising the account of a customer service system maintenance vendor, leveraging legitimate identities and normal operational activities as cover. Over a 78-day attack period, they attempted to gain access permissions to the customer service knowledge base and quality inspection systems. Despite generating over 2,000 related alerts during this time, these warnings failed to receive sufficient attention due to various reasons. The anomaly was finally detected during a routine security inspection before the Spring Festival holiday.
The Illusion of a Perfect Defense System
Forensic investigations revealed that attackers stealthily infiltrated the internal network using a vendor’s system maintenance account. Throughout the attack, our security systems continuously generated alerts but consistently failed to prevent the attack:
- When the attacker first logged in via VPN, SIEM produced a “low-risk” alert because the source IP came from a trusted vendor network segment using legitimate VPN channels.
- Three weeks later, when this account executed PowerShell commands late at night, EDR alerted again. However, since these were common system management commands and coincided with an impending system upgrade window, the alert was marked as “ignorable”.
- It was not until the pre-Spring Festival routine security inspection that we discovered this account’s abnormal attempts to access the customer service knowledge base and quality inspection systems.
This compels us to reconsider: Is our meticulously deployed layered defense system truly as impregnable as imagined?
Modern Attackers’ Sophisticated Strategies
What makes this incident particularly thought-provoking is not just the defense failures, but the advanced techniques demonstrated by the attackers. They carefully constructed a perfectly “compliant” intrusion scenario:
# The Fatal Weakness of Traditional Alert Judgment
def is_suspicious(event):
if event.source in trusted_sources and \
event.credentials.valid and \
event.behavior.matches_normal_ops:
return False # Seemingly reasonable judgment that cannot withstand scrutiny
return True
Modern attackers have long understood the blind spots in such simplistic logic. They no longer attempt to breach firewalls directly, but patiently seek out and exploit trusted identities and channels. They leave no obvious traces of malicious programs, instead perfectly mimicking normal operational behaviors.
The “Fragmented” Dilemma of Response Systems
More concerning was the dispersion of alert information. In this case, critical but overlooked signals included:
- Timing: “System access outside maintenance windows”
- Access: “First-time access to unauthorized systems”
- Operation: “Abnormal privilege probing behaviors”
- Location: “Access from unconventional IP address segments”
This information was scattered across VPN logs, EDR alerts, system audits, and other disparate systems, preventing the complete attack chain from being pieced together. The result: The attack persisted for 78 days before detection, generating over 2,000 related alerts with less than 20 hours of effective analysis time.
This significant delay exposes the fatal weakness of traditional linear response processes: When facing modern attackers’ concurrent assaults, our analytical capabilities have become the insurmountable bottleneck.
Breakthrough Practices: From Ideal to Reality
Following this incident, we began improving our detection and response systems. Frankly, this process proved more challenging than anticipated. It took approximately six months to gradually resolve the primary issues.
The initial tasks were fundamental yet labor-intensive:
Regarding logs, multiple problems emerged during investigation:
- Older systems generally exhibited poor log quality with frequent missing critical information
- Inconsistent timestamp standards across different systems caused correlation analysis difficulties
- Storage cost pressures made complete audit logs (often reaching terabyte levels) prohibitive
Account governance also revealed historical legacy issues. System management accounts, temporary accounts, departed employees’ accounts… Cataloging these proved time-consuming. The failure to implement basic account lifecycle management was indeed worthy of reflection.
After addressing foundational issues, we optimized alert quality. This process encountered numerous obstacles:
- Initially attempting overly granular rules resulted in alert volume explosions and high false-positive rates
- Subsequent filtering of obvious false positives directly reduced alert volume by 60%
- Through continuous tuning, we finally improved effective alert rates from 10% to 30%
Vendor management also exposed multiple problems:
- Approximately 20% of vendor account statuses were ambiguous, requiring re-confirmation of permission sources and responsible parties
- Some accounts had excessive permissions with obvious security risks
- Permission consolidation efforts faced implementation challenges, requiring balance between security and operational efficiency
Enhancing emergency response efficiency proved most challenging. Original response manuals were overly lengthy with limited practical value. We focused on clarifying three core issues:
- Identification of primary responders
- Clear escalation paths
- Cross-department collaboration mechanisms
Practical implementation showed noticeable improvements. However, certain difficulties persist:
💡 Outstanding Issues
- Human resource constraints, particularly in implementing 24/7 response mechanisms
- Heavy technical debt from legacy systems
- Continued need for cross-departmental collaboration efficiency improvements
The most significant realization is that security construction requires gradual progression. Blind pursuit of perfect solutions often backfires. Particularly regarding cross-department collaboration, beyond institutional processes, daily trust-building remains essential.
As frontline practitioners, we fully appreciate the difficulty of these changes. However, as this case demonstrates, traditional defense mindsets struggle against modern attackers’ sophistication. Fortunately, this incident enabled timely identification of defense system shortcomings. This not only prevented greater losses but also charted the course for future security development.
Only through continuous innovation and timely evolution can we gain the advantage in this silent war. Most crucially, we must maintain constant vigilance while perpetually refining and optimizing our security defense systems.
Digidations: Reshaping Incident Response Through Continuous validation
This case demonstrates how Cyritex helps enterprises establish more efficient incident response systems when facing complex attacks:
Identifying Fundamental Operational Issues
Through continuous simulation of real attack scenarios, we help enterprises detect and confirm issues such as frequent missing key log information, inconsistent timestamp standards, and excessive SIEM alert noise as seen in this case. By validateing indisputable attack simulations, we promote subsequent rectifications and optimizations, with retesting confirming issue resolution.
Detection Capability validation and Optimization
Through continuous simulation of real attack scenarios, we help enterprises identify blind spots in existing detection systems. Unlike traditional penetration testing, our validation is more systematic and sustained: simulating lateral movement post-vendor system compromise, abnormal operations using legitimate credentials, fragmented attack chains, etc. These are scenarios easily overlooked by traditional security systems. Practice shows this continuous validation approach can improve enterprise alert accuracy by over 30%.
Response Process Optimization
Accurate detection alone is insufficient—swift response is paramount. Through continuous attack simulations, we help enterprises identify and resolve efficiency issues in response processes. For instance, in this case, better integration of alert information across systems and establishing smoother cross-department collaboration mechanisms might have prevented the 78-day attack persistence. Our clients generally report 60%+ reductions in average response times through process optimization.
Continuous Improvement Mechanisms
Unlike traditional one-time assessments, we emphasize establishing closed-loop continuous improvement, including:
- Regular comprehensive capability evaluations
- Timely identification and validation of new attack techniques
- Continuous optimization of response strategies based on practical experience
- Building security knowledge bases to facilitate enterprise-wide experience accumulation