Email has been the backbone of business communication for decades and as such, it remains the attacker’s favorite doorway into an organization.
Phishing, Business Email Compromise (BEC) and supply-chain attacks continue to rise, with adversaries leveraging AI and compromised accounts to bypass legacy defenses. This presents many challenges for CISOs, IT Directors and SOC teams alike: it seems pretty clear that threats are evolving faster than traditional email security can keep up.
Defending against email threats requires more than filtering, static rules, or a traditional secure email gateway (SEG). It also needs to factor in behavioral intelligence and adaptive threat detection as well as a security culture that minimizes human risk.
Email Is Still the #1 Attack Vector and Attacks Are Getting Smarter
Despite investment in SEG technologies and built-in cloud protections, malicious emails still slip through. Attackers know that employees are the largest attack surface, so they continue to refine their tactics.
Key shifts in the last year include:
- Phishing volumes continue to rise. Organizations have reported significant increases in phishing email volume in recent months, particularly campaigns targeting finance teams, IT admins and executives.
- Attackers increasingly use AI. AI now helps attackers craft highly convincing emails, mimic internal communication styles, and personalize messages at scale. From context-aware phishing to multilingual BEC attempts, AI is amplifying the sophistication of threats.
- Compromised accounts are driving more attacks. More phishing emails now originate from legitimate but compromised sender accounts, making them far harder for traditional filters to catch. These attacks often imitate partners, vendors or internal staff, bypassing reputation-based controls.
- Shift from attachments to URL-driven attacks. Malicious links that point to weaponized login pages, fake cloud storage portals, or malware-hosting infrastructure now dominate email-based attacks. These URLs often mutate rapidly, making signature-based tools ineffective.
- Supply-chain phishing is surging. Adversaries increasingly infiltrate trusted third-party systems, then use legitimate email domains to distribute malicious content. These threats frequently appear “normal” to existing filters.
The result is that even organisations with strong email security are seeing dangerous messages land in inboxes.
Why Legacy SEGs and Native Filters 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.
Email Security Must Evolve
CISOs, IT leaders and SOC teams face a rapidly shifting threat environment in which AI-generated phishing is escalating, compromised accounts increasingly bypass legacy controls, cloud email environments demand modern, behavioral detection; and organizations are consolidating around Microsoft 365, making layered security essential.
Behavioral AI for Modern Email Threats
KnowBe4 Defend Advanced Inbound Email Threat Defense is engineered to catch the sophisticated, socially engineered phishing attacks that SEGs and basic email filters miss.
Defend augments Microsoft 365’s native protection by analyzing emails through a behavioral lens, rather than relying solely on signatures or policies. Here’s what that means for your security posture:
Behavioral AI detection
Defend evaluates how an email behaves:
- Does the writing style match the sender?
- Is the message type unusual for this relationship?
- Is the domain behaving differently than normal?
- Does the URL behavior or intent appear suspicious?
This approach lets Defend stop:
- AI-crafted phishing messages
- BEC attempts with no payload
- Vendor email compromise
- Zero-day phishing campaigns
- Malicious URLs embedded in seemingly harmless messages
Layered protection without complexity
Defend integrates natively with Microsoft 365, allowing organizations to:
- Migrate away from costly SEGs
- Maintain – or exceed – previous levels of protection
- Reduce administrative overhead
- Improve detection accuracy with minimal operational impact
Continuous learning and adaptation
Because Defend is behavioral and self-learning, detection improves over time as it ingests organization-specific patterns and global threat insights.
Immediate remediation and simplified workflows
Security teams can quickly review flagged emails, take action or automate remediation, reducing alert fatigue and improving response times.
The Human Factor Still Matters
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.
Combining KnowBe4 Defend with KnowBe4’s Human Risk Management approach ensures that organizations address both sides of the risk equation: technical protection to stop dangerous emails and human-centred training to help employees recognize and avoid threats when they occur.
This dual-layer strategy creates a more resilient organization and significantly reduces the likelihood of a successful compromise. As attackers evolve, so must defense strategies. The organizations 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.
