Recent trends in initial access techniques: Vulnerability exploits top the list

How evolving tactics like vulnerability exploits and AI-powered phishing are shaping cybersecurity risks

Takeaways:

• Initial access techniques are evolving fast, with attackers leaning heavily on vulnerability exploits, social engineering, credential‑based VPN attacks and AI‑powered phishing.
• Deloitte’s most recent Cyber Threat Trends Report highlights these four access vectors as the most impactful across industries.
• AI, automation and cloud‑based tools are making these initial access methods easier and faster for attackers to deploy.
• Organizations can dramatically reduce risk by prioritizing visibility, rapid detection and layered defenses.
• Barracuda solutions can help reinforce defenses at every entry point, from email to applications to cloud‑connected infrastructure.

Cybercriminals are always looking for the easiest way in, and in recent years they’ve gotten smarter and faster. Understanding the initial access techniques that they use is critical for anyone responsible for cybersecurity. If you know what techniques are trending and can implement strategies to block them, you can dramatically reduce your cyber risk.

Deloitte’s most recent Annual Cyber Threat Trends Report delivers a wealth of valuable insights into how adversaries operated across industries in 2024. The report covers threat actors, major infiltration vectors, ransomware innovations, underground economy shifts and more. In this post, we’ll focus on what they uncovered about trending initial access techniques.

Vulnerability exploitation

Attackers continued to pounce on everything from brand‑new zero‑days to years‑old, unpatched flaws. Deloitte highlights that ransomware groups such as Clop exploited multiple zero‑day vulnerabilities late in the year, with many major breaches tied back to long‑known bugs that organizations still hadn’t addressed.

This matches broader industry reporting. As Infosecurity Europe notes, “Vulnerability exploitation is emerging as a primary initial access vector … accounting for 33% of all hacks in 2024.”

Advanced application security and API protection platforms like Barracuda Application Protection can help block exploit attempts in real time and shield vulnerable systems, even when patching takes time. Layered web application firewall, bot defense and continuous scanning help reduce exposure windows.

Social engineering

Attackers didn’t just exploit systems. Increasingly, they exploited people. Deloitte describes a sharp rise in blended social engineering attacks, especially combinations of vishing and business email compromise (BEC), where adversaries impersonated clients via phone and email and tricked help-desk personnel into resetting credentials.

This aligns with insights from the Initial Access Trends 2025 analysis on Medium, which notes that, “Adversaries are investing more in human‑centric operations that bypass technical safeguards altogether.”

Barracuda Email Protection, which includes AI‑enhanced account takeover detection and real‑time impersonation defense, can stop fraudulent emails, suspicious login behavior and domain spoofing before they reach your users. Security Awareness Training adds an extra human firewall.

VPN exploitation and stolen credentials

Deloitte’s team saw a major shift in how attackers break into corporate VPNs. Instead of brute‑forcing passwords, adversaries increasingly used deliberately stolen credentials sourced from the dark web, infostealers and access brokers. They also used cloud‑based services as proxies, making their activity harder to detect.

Infosecurity Magazine confirms the rise of credential‑driven attacks: “Stolen credentials jumped from 10% to 16% … becoming the second most common technique behind vulnerability exploitation.”

Barracuda Network Protection includes robust zero-trust access capabilities that help you enforce strong authentication, minimize VPN exposure, and inspect traffic from remote connections. Continuous identity risk evaluation can catch suspicious login patterns early.

AI‑enhanced phishing

Phishing didn’t go away, but it certainly evolved. Deloitte reports that threat actors can now generate 1,000 phishing emails in under two hours for as little as $6, thanks to generative AI. The result? A massive 1,265% spike in phishing attacks during 2024.

Barracuda Email Protection is designed specifically to use AI and machine learning to detect LLM‑generated phishing, deepfake‑style impersonations and targeted spear‑phishing campaigns. Automated remediation tools help remove malicious emails instantly across all inboxes.

Conclusion

2024 proved that attackers don’t need to break down the door; they just need to find the one you haven’t locked yet. With vulnerability exploits accelerating, social engineering getting more personal, credentials flooding dark‑web markets, and AI powering ultra‑believable phishing, initial access has never been more dynamic.

Deloitte’s insights reinforce the need for cybersecurity professionals to implement strategies and solutions that deliver visibility, automation and protections that adapt as quickly as attackers do.

The BarracudaONE platform integrates layered security across email, apps, remote access, APIs, and cloud workloads, helping you stay ahead of evolving initial access techniques without overwhelming your IT and security teams.