Release Date: 15 Sep 2026
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Internet-edge devices such as VPN appliances, firewalls, routers and remote access systems are critical gateways between the Internet and an organisation’s internal network. If compromised, attackers may gain access to internal systems, steal account information, maintain a long-term presence, or go on to cause a data breach or launch a ransomware attack.
In the intelligent era, cyber security requires not only technical safeguards, but also staff vigilance and continuous risk management. Organisations should regularly inventory all externally accessible network devices and management interfaces, review vulnerabilities, configurations and account status, and continuously monitor for abnormal activity. Drawing on recent incidents, this security blog explains why patching is only the first step and what follow-up measures organisations should take afterwards.
Japanese government incident highlights risks to Internet-edge devices
Japan’s Digital Agency announced that its Government Solution Service (GSS) had been compromised through a vulnerability in VPN-related equipment. Approximately 246,000 records of personal data may have been affected, involving government personnel, contractors and partners. The incident shows that, even where a large organisation has deployed multiple security measures, attackers may still gain initial access and cause a large-scale data breach if Internet-edge devices remain vulnerable or account credentials are stolen.
Incidents of this kind show that Internet-edge devices have become a common entry point into organisations. Attacks targeting VPNs, firewalls and remote access services have continued to increase in recent years. For example, some recently disclosed high-risk vulnerabilities affecting Fortinet firewall products have been actively exploited by attackers; devices that have not yet been patched may therefore remain exposed.
Risks may persist after patching
Even when an organisation patches a vulnerability promptly, the risk may not disappear. A system update can close the vulnerability, but it does not automatically remove access paths established by an attacker before the patch was applied. The attacker may already have entered the network, obtained accounts or credentials, and continued operating through malicious accounts, backdoors or other persistence mechanisms.
The FortiBleed credential leak disclosed this year is one example. Login credentials for some Fortinet network devices were suspected to have been exposed, potentially affecting more than 70,000 devices worldwide. The main risk in such a leak is that authentication data exposed before a vulnerability was patched may remain valid afterwards, allowing attackers to sign in again and continue their intrusion.
Organisations should therefore not only patch vulnerabilities, but also review account security, active sessions, credentials and system logs to determine whether any unauthorised access has occurred. Depending on the risk, they should reset credentials, revoke active sessions and conduct an incident investigation.
Follow-on risks requiring attention
If Internet-edge devices are compromised, organisations may face the following risks:
- Continued misuse of accounts, passwords and other authentication information;
- Attackers remaining undetected in the network for an extended period while quietly gathering information;
- The use of compromised accounts to access other systems, move laterally and escalate privileges; and
- Data breaches, ransomware attacks or business disruption.
In other words, the compromise of an Internet-edge device is often the beginning of an attack chain, not the end. After gaining initial access, attackers may expand their reach, establish persistence, and cause more serious harm to operations and data.
Strengthen checks ahead of major events
Major conferences, exhibitions, sporting events and important festivals often increase an organisation’s public exposure and may also heighten the risk of cyberattacks. Attackers commonly prioritise Internet-facing VPNs, firewalls and management interfaces, exploiting known vulnerabilities, misconfigurations or leaked account credentials. Pre-event security checks should therefore address not only system availability but also signs of compromise and incident response readiness.
HKCERT recommends that organisations recheck relevant devices and systems before important events, including:
- The status of vulnerability patching and firmware updates;
- Account and access-rights settings;
- Abnormal login records;
- Suspicious network traffic and data transfers; and
- Incident response and business continuity arrangements.
HKCERT recommendations: patching, verification and continuous monitoring
To reduce the risk of attacks on Internet-edge devices, and of compromised accounts or persistence mechanisms continuing to be used after patching, organisations should take the following measures:
- Prioritise patching of high-risk vulnerabilities known to be actively exploited;
- Enable multi-factor authentication (MFA) for VPNs, management interfaces and privileged accounts;
- Regularly review accounts and access rights, and disable accounts that are no longer used or are unrecognised;
- If account information is suspected to have been exposed, immediately change passwords and related credentials, and revoke active sessions;
- Continuously monitor abnormal logins, changes to privileges and suspicious data transfers; and
- After patching, investigate whether systems have already been compromised or contain backdoors, malicious accounts or other persistence mechanisms.
Establish continuous monitoring
VPNs, firewalls and other Internet-facing network devices are among an organisation’s most important network gateways and are frequently targeted by attackers. Vulnerability patching is an essential risk-control measure, but it should not be treated as the end of the process. A complete protection process should also include asset inventory, account and credential management, monitoring for abnormal behaviour, intrusion investigation, incident response and business continuity arrangements.
Organisations can adopt an “Assume Breach” security mindset. After patching, they should proactively verify whether accounts, credentials and internal systems have been compromised, and search for backdoors, malicious accounts and other persistence mechanisms. Combining patching, verification and continuous monitoring is the only way to reduce more effectively the risk of attackers maintaining a long-term presence or regaining access.
To report an information security incident to HKCERT, please call the 24-hour hotline on (852) 8105 6060. For other enquiries, please contact HKCERT by email at [email protected].
Data BreachVirtual Private Network (VPN)
