How can businesses respond to phishing emails from legitimate domains?

　　As enterprises become increasingly information-driven, email has become a crucial tool for daily communication, customer contact, and business collaboration. However, while email systems offer convenience, they have also become a significant entry point for cyberattacks. In recent years, a more insidious attack method has emerged—phishing emails originating from legitimate domains. These emails often utilize real domains or compromised email accounts, appearing highly credible and easily lowering employees' guard, leading to account leaks, financial losses, or data theft. For enterprises, establishing robust identification and protection mechanisms has become a vital aspect of information security management.

　　Phishing emails originating from legitimate domains typically refer to emails sent by attackers who do not forge domains but instead compromise real email accounts, register domains highly similar to the company's, or use stolen third-party corporate email addresses. Because the email source appears to be a "trusted domain," many traditional spam filtering rules are unable to intercept them, increasing the probability of a successful attack. Attackers often mimic internal company notifications, financial emails, system upgrade reminders, or partner information, inducing users to click on links, download attachments, or enter account passwords to achieve their attack objectives.

　　To combat these phishing emails, enterprises should begin by improving the security configuration of their email systems. A robust email authentication mechanism can significantly reduce the occurrence of spoofed and suspicious emails. When deploying an email system, enterprises should configure three common email security authentication mechanisms: SPF, DKIM, and DMARC. SPF verifies the legitimacy of the mail sending server, DKIM verifies whether the email content has been tampered with, and DMARC defines the server's strategy when email authentication fails, such as isolation or outright rejection. These technologies effectively improve the ability to verify the source of emails.

　　Besides email authentication technology, enterprises also need to strengthen domain name security management. Many phishing attacks register domains very similar to the company name, such as replacing the letter "l" with the number "1" or adding extra characters to mislead users. Enterprises can reduce the risk of impersonation by registering common, similar domain names and regularly monitor the internet for new domains highly similar to their brand. Once suspicious domains are discovered, timely complaints or legal action can be taken.

　　Email gateway security is also a crucial part of the protection system. Enterprises can deploy professional email security gateways to scan and analyze all emails entering the company mailbox. Email gateways typically possess functions such as anti-spam, malicious attachment detection, URL security detection, and behavioral analysis. When emails contain suspicious links or unknown attachments, the system can automatically isolate or flag them, thereby reducing the risk of employees accidentally clicking on them.

　　For links in emails, enterprises can also use link rewriting or sandbox detection technologies. When an employee clicks a link in an email, the system will first redirect the link to a security detection platform, analyzing the webpage behavior in a sandbox environment. If a phishing page or malicious script is detected, the system will automatically block access and issue a security warning. This method can effectively prevent employees from accessing fake login pages.

　　Employee security awareness training is also an important measure to prevent phishing emails. Many attacks succeed not because of technical vulnerabilities, but because employees lack the ability to identify them. Enterprises should conduct regular cybersecurity training, explaining to employees the characteristics of common phishing emails, such as unusually urgent financial requests, payment notifications that do not conform to business procedures, attachments from unknown sources, and email links that require account passwords. Through case studies and simulations, employees can gradually improve their vigilance.

　　In daily management, enterprises can also establish email verification processes. For sensitive operations such as fund transfers, contract changes, or account modifications, secondary confirmation should be required via telephone, internal systems, or instant messaging tools, rather than relying solely on an email. This makes it difficult for attackers to successfully send phishing emails and carry out fraudulent activities.

　　Log monitoring and anomaly behavior analysis are equally crucial. Enterprises can analyze email sending and login behavior through security monitoring systems, such as a large number of emails sent in a short period, login requests from unusual countries or regions, and a sudden increase in email forwarding rules. These behaviors are often early signs of email compromise. Timely detection and action, such as resetting passwords and enabling multi-factor authentication, can effectively prevent further attacks.

　　Regarding account security, enterprises should implement multi-factor authentication mechanisms whenever possible. Even if attackers obtain employee passwords through phishing emails, they cannot log into the corporate email system without a second layer of authentication, such as mobile verification codes or security tokens. This significantly improves account security.

　　Furthermore, enterprises should establish a robust emergency response mechanism. If an employee receives a suspicious email or accidentally clicks on a phishing link, it should be reported to the information security department immediately. Security teams can quickly inspect relevant email accounts, including checking login records, email forwarding rules, and abnormal sending records. They can also perform batch searches of emails with identical content through the email system to prevent more employees from being affected.

　　For large enterprises, combining this with a threat intelligence platform can further enhance protection capabilities. Threat intelligence platforms continuously collect malicious domains, phishing websites, and attacking IP addresses globally and synchronize this information to the enterprise's security systems. When employees receive emails from known malicious domains, the system can automatically block them.

　　Overall, combating phishing emails from legitimate domains requires a multi-layered protection strategy, including technical protection, management systems, and employee awareness training. A single measure is often insufficient to completely solve the problem, while a combination of email authentication, email gateways, link detection, security training, and multi-factor authentication can significantly reduce the risk of phishing attacks on enterprises.