For decades, email has been the backbone of corporate communications and for precisely this reason, it remains the attacker’s preferred gateway into organisations. Phishing, Business Email Compromise (BEC), and supply chain attacks continue to increase, with adversaries using AI and compromised accounts to bypass classic protection mechanisms. The rapid evolution of threats presents significant challenges for CISOs, IT Directors, and SOC teams, highlighting the inability of traditional email security to keep pace.
Attacks are getting smarter, not necessarily more complex
It is striking how much attacks have changed in the past year. On the one hand, the volume of phishing is noticeably increasing, especially in campaigns against finance departments, IT administrators, and executives. On the other hand, AI ensures that attacks appear more convincing: emails can be created in the style of internal communication, content is personalized and rolled out on a large scale – right up to context-aware phishing and multilingual BEC attempts.
At the same time, many attacks today no longer originate from ‘obviously’ malicious sources, but from legitimate, yet compromised, sender accounts. This makes detection significantly more difficult, as reputation and domain signals suddenly look clean. In addition, the focus is shifting from attachments to URL-based attacks. Links lead to prepared login pages, fake cloud portals, or malware infrastructure and often change so quickly that signature-based methods fail. It becomes particularly delicate when supply chain phishing occurs via trusted third-party systems, and legitimate domains are abused for distribution. The result: even organisations with supposedly solid email security see dangerous messages landing in their inboxes.
Why classic filters and SEGs aren’t enough
Traditional SEGs rely heavily on static rules, signatures, domain reputation and known attack indicators. While they can block commodity attacks, they often struggle with modern phishing patterns. For instance, AI-generated content is unique, making signature-based detection ineffective. In addition, the BEC attacks that can catch employees out to make money transfers or to buy gift cards don’t actually contain links or attachments, so would appear benign to an SEG.
Furthermore, compromised real accounts use clean infrastructure, bypassing domain-based filtering and malicious URLs can evade traditional scanning by changing rapidly. The bottom line is static policy-based systems can’t adapt fast enough to attacker iteration.
At the same time, the market is shifting: more organizations are moving away from expensive, legacy SEG appliances and consolidating email under Microsoft 365. Native tools like Exchange Online Protection (EOP) are solid foundations but not enough alone for today’s threat landscape.
Behaviour-based AI and the Human Factor
A modern defense principle relies not only on known signatures but also on behavioral and contextual signals. For example, it checks whether the writing style matches the sender. Is the message unusual for this relationship? Is a domain behaving differently? Does a URL seem suspicious in its intent or behavior? This focus on plausibility addresses the attack forms that classic filters often overlook. For example, AI-supported phishing, BEC without payload, Vendor Email Compromise, zero-day phishing, or malicious links in seemingly innocuous messages. Crucially, this detection continuously learns and adapts to organisation-specific patterns as well as global threat intelligence, instead of just processing static rules. Additionally, fast review and remediation workflows are important to reduce alert fatigue and improve response times.
Even with advanced behavioral AI in place, attackers still target people. A strong security culture reinforced by awareness, simulated phishing, and real-time teachable moments remains essential. Resilient email security requires both technical protective measures and human risk management.
This dual-layer strategy creates a more resilient organisation and significantly reduces the likelihood of a successful compromise. As attackers evolve, so must defense strategies. The organisations that embrace layered behavioral AI, combined with strong security awareness, will be the ones best equipped to withstand the next wave of phishing, BEC and social-engineering attacks.
