What Is an Attack Surface?

An attack surface is the total number of possible ways an attacker can access your systems, networks, or data. It includes all vulnerabilities, misconfigurations, exposed services, and user access points that can be targeted. Attack surfaces are made up of multiple attack vectors, such as open ports, outdated software, exposed credentials, and phishing emails. The larger the attack surface, the more opportunities an attacker has.

This blog explains what makes up an attack surface, the role of attack vectors, and how organizations can reduce risk by analyzing and prioritizing exposures.

What Is an Attack Vector?

An attack vector is a path or method used by threat actors to breach a system, steal data, or disrupt operations. It’s how an attacker gets in, whether by exploiting a software vulnerability, abusing misconfigurations, or targeting human behavior like phishing.

Attack vectors can be technical (e.g., zero-day exploits, drive-by downloads) or social (e.g., credential theft, malicious email attachments). Once successful, they allow attackers to deliver payloads, escalate access, or move laterally within a network.

Relation Between Attack Vector and Attack Surface

The number and variety of attack vectors directly shape an organization’s attack surface, the complete set of potential entry points that threat actors can exploit. Each attack vector adds to this surface, increasing the pathways available for compromise.

Reducing or hardening these vectors is essential for shrinking the overall attack surface and lowering cyber risk.

In the following section, we examine the most common attack vectors and how each one contributes to the broader attack surface.

Common Types of Cyber Attack Vectors and Real-World Cases

Phishing and Social Engineering

Phishing Emails

Phishing emails are a common attack vector used to gain initial access by tricking users into revealing sensitive information or interacting with malicious content.

• Example: Storm-0558 (China-Linked) – Microsoft Email Breach (2023) [1]

• Vector: Phishing targeting Microsoft support staff or token misuse.

• Impact: Gained access to Outlook email accounts of U.S. government agencies.

• Significance: Exploited forged authentication tokens after initial credential theft, showing how phishing can be the first domino.

Malicious Email Attachments

Embedded malware in files like Office documents or PDFs is a common attack vector used to gain unauthorized access to organizational networks.

• Example: Bumblebee Loader Campaign (2024) [2]

• Vector: Email with ISO attachment (evasion of Microsoft macro defenses)

• Payload: The ISO mounted a LNK (shortcut) file that executed a script downloading Bumblebee malware.

• Result: Gave attackers initial access and served as a staging tool for ransomware affiliates.

Fake Login Pages & Credential Harvesting

Fake login pages and credential harvesting are prevalent attack vectors used to steal usernames, passwords, and MFA codes for unauthorized access to organizational networks.

• Example: Storm‑2372 Device-Code Phishing (Aug 2024 – Feb 2025) [3]

• What: A nation-state-tied campaign (suspected Russian-aligned) targeting governments, NGOs, and enterprises worldwide.

• How: The attacker initiates a legitimate OAuth "device code" flow by prompting victims, via messages mimicking Teams, WhatsApp, or Signal, to enter a code into a convincing login UI.

• Harvest: Users input the device code believing it's safe, but Storm‑2372 captures the authentication tokens and reuses them to gain access without passwords.

Credential-Based Entry 

Stolen or reused credentials are a common attack vector that allows adversaries to bypass authentication and gain direct access to systems or accounts.

Stolen Credentials & Account Takeover

Attackers use harvested, bought, or reused credentials to log in.

• Example: Snowflake Cloud Breach (Mid‑2024) [4]

• Vector: Attackers used credentials stolen via infostealer malware to log into over 160 Snowflake customer accounts, most lacked MFA .

• Impact: Sensitive data from clients like AT&T, Ticketmaster, Santander was accessed and extorted, AT&T paid a ransom of ~$370,000.

• Significance: Access granted with stolen credentials + no MFA, even without sophistication (no phishing/vulnerabilities).

Brute-Force and Credential Stuffing

Automated attempts to guess credentials across login surfaces.

• Example: 23andMe Data Breach via Credential Stuffing (Oct 2023 → Analyzed 2025) [5]

• Vector: Attackers used a “credential smear” attack, automated login attempts across known email/password combos.

• Result: 14,000 accounts directly compromised, which then cascaded to expose ~5.5 million users’ genetic data.

Exploitation of Known Vulnerabilities (CVEs) and Zero-Day Attacks

Exploiting Known Vulnerabilities

Exploiting outdated or unpatched software, such as VPNs and web servers, remains a prominent attack vector for gaining initial access through known and emerging vulnerabilities.

These real-world incidents from 2024 and 2025 show how attackers continue to exploit both known and newly discovered vulnerabilities to gain initial access.

• Example: A critical unauthenticated RCE flaw in Fortinet’s FortiOS SSL VPNs (CVE-2024-21762)

• Attackers: State-linked actor Volt Typhoon exploited it to deploy custom malware and backdoors across global networks [6].

• Why It’s Important: Despite patches being available, real-world exploitation continued due to slow patching and PoC leaks, showing how unpatched internet-facing VPNs actively enable initial compromise.

Another high-profile case from 2025 further illustrates the danger of delayed patching and rapid exploitation of disclosed flaws.

• Example: A critical buffer-overflow bug in Ivanti’s VPN appliances (CVE-2025-22457), disclosed February 2025.

• Attackers: Chinese-linked espionage group UNC5221 leveraged it in mid-March to deploy in-memory malware (e.g., TRAILBLAZE, BUSHFIRE) and achieve RCE [7]. 

• Takeaway: True zero-day post-patch exploitation demonstrates risk when organizations lag in applying critical updates.

Zero-Day Exploits

Attacks against unknown or unpatched flaws with no vendor fix.

• Example: A remote code execution zero-day in the WebDAV service of Windows servers (CVE-2025-33053), patched in June.

• Attackers: APT “Stealth Falcon” used it via malicious .url files hosted on a WebDAV server to execute malware on target systems, including a defense contractor in Türkiye [8].

• Significance: Illustrates how zero-days in legacy Windows components serve as stealthy initial access vectors with no human interaction needed.

Insider Threats

Malicious or Coerced Insiders

Authorized users granting access intentionally or under pressure.

• Incident: A huge dataset of 2.87 billion Twitter/X profiles was leaked online. The leaker, a user named “ThinkingOne”, claimed the breach was “almost certainly” the work of a disgruntled former employee following layoffs under Musk [9].

• Scale: The dataset included public and private user information dating back to the platform’s inception.

• Attribution: No proof beyond the leaker’s claim, but internal access by a terminated staffer is suspected.

• Significance: A disgruntled former employee, who had not been fully offboarded after being laid off, retained access to internal systems and used it to aggregate and leak large volumes of user data. 

Unintentional Insiders

Users unknowingly enable access (e.g., reusing passwords, clicking malicious links).

Drive-by and Browser-Based Attacks

Drive-by Downloads

Malware installation triggered by simply visiting a compromised or malicious site.

• Example: FakeBat Loader via Drive‑By Download (August 2024)

• Technique: Users visited compromised or malware-laced websites (including fake software download pages). Once opened, JavaScript triggered a download (“drive-by”) that installed FakeBat Loader, a malware loader disguised as legitimate software updates.

• Outcome: FakeBat dropped additional payloads like IcedID, RedLine, and SmokeLoader, paving the way for ransomware or data theft.

• Significance: Shows how pure drive-by downloads (with no email click required) are used to deliver sophisticated malware in an automated, “invisible” manner.

Browser Exploits & Web Injection

Malicious scripts injected into sites or loaded via ads to compromise endpoints.

• Example: Over 269,000 legitimate websites were infected with obfuscated JavaScript (JSFireTruck) [10].

• Technique: When visitors arrived via search engines, scripts redirected them to TDS networks that delivered fake CAPTCHAs, fake updates, or malware payloads.

• Outcome: Network-wide distribution of malware, scams, and exploit kits, indicative of highly automated, large-scale browser attacks.

• Significance: Highlights the ongoing scale and stealth of modern browser exploits, compromised sites used as malware platforms rather than isolated phishing campaigns.

Four Steps of Organizational Attack Vector Analysis 

It focuses on identifying the methods and entry points threat actors can use to gain initial access to systems. By understanding these vectors, whether technical, such as software exploits, or human-driven, like phishing, organizations can assess how adversaries might breach their defenses and prioritize mitigation efforts accordingly.

• Step 1. Threat Identification

• Step 2: Mapping Out All Entry Points

• Step 3: Step 3: Vulnerability Assessment

• Step 4: Step 4: Risk Assessment

Each step is outlined below.

Attack Vector Analysis in Action: A Real-World Case Study

An enterprise SaaS company, AcmeCorp, provides collaboration tools to Fortune 500 clients. With recent headlines of supply chain breaches and VPN exploits, AcmeCorp's security leadership initiates an attack vector analysis to identify their most exposed entry points and reduce risk before the next red team engagement.

Step 1: Threat Identification

AcmeCorp begins by evaluating the threats most likely to target their environment. The security team reviews recent threat intel reports, internal incident trends, and industry-specific attack patterns.

Findings include:

• Several production S3 buckets are misconfigured to allow public read access.
• The organization uses Fortinet SSL VPNs, which were affected by CVE-2023-27997, recently exploited in the wild.
• Employees reported receiving phishing emails mimicking internal HR tools.
• A recently offboarded engineer still had active GitHub repository access.
• SOC observed anomalous login attempts from Southeast Asia into the Okta portal, likely testing credential-stuffing lists.
• Threat reports flag EvilProxy phishing kits targeting SaaS companies like AcmeCorp to steal MFA tokens.

Step 2: Mapping Out All Entry Points

Next, AcmeCorp maps all internal and external surfaces that could serve as entry points for the identified threats.

They assess:

• Application layer: Outdated staging environments with exposed login panels

• Infrastructure layer: Unmonitored routers at branch offices, VPNs with default admin panels exposed

• Identity layer: Dormant but privileged accounts in their Okta directory; lack of enforced MFA for internal DevOps tools

• Human layer: Developers using personal email for test credentials; weak phishing awareness scores in sales

• Third-party risk: A third-party marketing vendor with direct database access

• Emerging tech: ML pipeline in production built by an external team, not yet assessed by security

Step 3: Vulnerability Assessment

With all entry points identified, AcmeCorp’s SecOps team runs a coordinated vulnerability scan across cloud infrastructure, user endpoints, and critical business systems.

Key activities:

• Vulnerability scanner identifies unpatched systems running vulnerable versions of OpenSSL and Apache

• Cloud security posture management (CSPM) tools flag critical misconfigurations in GCP IAM and storage

• Red teamers simulate a phishing email that leads to a fake Okta login page, successfully capturing credentials and session cookies via EvilProxy. 

• Offensive team also exploit CVE-2023-27997 on a VPN device that hadn’t been patched since last quarter’s update freeze

Step 4: Risk Assessment

Key factors to consider are the following.

• Exploitability: Is there a public exploit? Is it being used in active campaigns?

• Asset criticality: Would a breach expose sensitive customer data or disrupt business operations?

• Blast radius: Could it lead to lateral movement, privilege escalation, or full system compromise?

AcmeCorp then evaluates the business impact and exploitability of each finding.

High-priority risks include:

• Publicly accessible dev instance with hardcoded admin credentials

• VPN exposure to a pre-auth RCE that can grant remote shell access

• Phishing + token theft combination that bypasses Okta MFA and grants access to internal systems

• Persistent access through dormant contractor accounts left over from an M&A integration

Each risk is scored based on:

• Business function (e.g., customer-facing systems vs. internal testing)

• Sensitivity of accessible data

• Likelihood of external exploitation based on threat intel

Result of Attack Vector Analysis

Within four weeks, AcmeCorp:

By conducting scenario-driven attack vector analysis, AcmeCorp not only reduced its attack surface, but also proactively closed vectors that could have been chained into a major breach.

Types Of Attack Surfaces

Earlier, we explained that an attack surface represents the full set of entry points, digital, physical, and human, that an attacker could exploit to gain unauthorized access, steal sensitive data, or disrupt operations. This includes all known, unknown, and potential attack vectors within an organization.

The broader and more complex the attack surface, the greater the risk, more systems to secure, more users to protect, and more opportunities for adversaries to break in. That’s why identifying, monitoring, and reducing the attack surface is essential to improving an organization’s overall security posture and resilience.

To better understand and manage exposure, attack surfaces are commonly categorized into three main types:

Digital Attack Surface

The digital attack surface includes all externally and internally accessible systems, services, and applications connected to your network. These are the technical components attackers can reach over the internet, via a partner connection, or through internal compromise.

It typically includes:

• Web applications and APIs

• Open ports and exposed services

• Cloud storage, misconfigured buckets, and SaaS platforms

• Public-facing servers and infrastructure

• Source code and exposed credentials (e.g., on GitHub)

• Shadow IT: unauthorized apps or devices deployed outside IT control

• Mobile and IoT devices with weak security controls

Physical Attack Surface

The physical attack surface includes any physical access point that could be used to compromise systems, steal equipment, or tamper with hardware.

Common examples:

• Unlocked server rooms or data closets

• Unattended workstations or laptops

• USB ports or removable media access

• Lost or stolen employee devices (e.g., phones, tablets, badges)

• Badge tailgating or social engineering at reception

Social Engineering Attack Surface

The social engineering attack surface refers to the human layer of an organization, employees, contractors, and even executives, who may be manipulated by attackers to unintentionally help carry out an intrusion. Unlike technical vulnerabilities, social engineering exploits trust, urgency, and human error to bypass established security controls.

Key vectors within this attack surface include phishing, insider threats, and social media exploits.

Phishing Attacks

Phishing remains one of the most common and effective social engineering techniques. Attackers send emails, texts, or direct messages that appear legitimate, tricking users into:

• Clicking on malicious links
• Entering credentials into fake login pages
• Downloading malware-laced attachments

Insider Threats

Insider threats involve trusted individuals, employees, contractors, or partners, who misuse their legitimate access. This may be:

• Malicious: A disgruntled employee intentionally leaking data or granting access to adversaries

• Negligent: An employee unknowingly reusing passwords or falling for a phishing link

Social Media Exploits

Attackers often use platforms like LinkedIn, X (formerly Twitter), or Facebook for:

• Reconnaissance: Gathering info on job roles, tech stack, or org charts
• Impersonation: Creating fake profiles to engage employees in phishing or pretexting
• Brand abuse: Spreading malicious links under the guise of a trusted brand account

Best Practices for Creating a Comprehensive Asset Inventory

Building an asset inventory is the starting point for understanding what makes up your attack surface. This includes identifying all systems, applications, and infrastructure, whether on-prem, cloud-based, remote, or third-party managed, that could potentially be targeted.

Include assets such as:

• Internet-facing services (e.g., VPN gateways, web apps, exposed APIs)

• Internal systems with lateral movement potential (e.g., domain controllers, shared file servers)

• Shadow IT resources or unmanaged SaaS accounts

• Cloud misconfigurations (e.g., overly permissive IAM roles, public S3 buckets)

To be effective, the inventory should be continuously updated, risk-prioritized, and enriched with threat intelligence. This ensures security teams have the context needed to detect exposures early, align defenses with business-critical assets, and respond to threats based on real-world relevance.

A well-maintained inventory isn't just a list, it’s a living map of where your organization is exposed.

The Process of Attack Surface Discovery 

Attack surface discovery is the first step in managing and reducing an organization’s exposure. It involves identifying all digital assets that could be exploited by attackers, across on-prem, cloud, and remote environments.

This includes endpoints, servers, databases, routers, cloud services, APIs, remote access points, and even social engineering targets. Here are the four key steps of attack surface discovery and validation.

Asset Inventory

Build a complete list of IT assets, including devices, applications, services, and data stores.

Access Point Identification

Detect exposed interfaces such as public-facing applications, VPNs, admin portals, and third-party integrations.

Vulnerability Detection

Identify exposed assets using tools like Picus Attack Surface Validation (ASV). ASV reveals potential entry points and provides business context to support exposure validation and calculate the Picus Exposure Score (PXS).

Threat Analysis and Validation

 Identifying exposed assets is only the beginning, understanding whether they can be exploited is what truly matters. That’s why validation is essential. It’s not just about confirming an attack vector, the initial access point, but also simulating what could follow if an attacker succeeds. 

With Breach and Attack Simulation (BAS), Picus Exposure Validation tests exposures in the context of full adversary campaigns, replicating real-world threat actor behavior and malware kill chains. This approach reveals whether your controls block early-stage tactics like initial access, and also later-stage techniques such as lateral movement, privilege escalation, or data exfiltration. 

As a result, an exposure initially marked “critical” based on global scores can be downgraded, or elevated, based on real risk to your environment.

How Can Organizations Prioritize Threats Based on Their Attack Surface Analysis?

To prioritize threats effectively, organizations must go beyond surface-level scoring and validate which exposures are truly exploitable in their environment. The process starts with a thorough attack surface analysis, identifying all assets and their potential exposure points, including systems, applications, and external interfaces.

Once the attack surface is mapped, potential threats should be assessed not only by severity scores like CVSS or EPSS, but by whether adversaries can exploit them in practice. 

This requires context: Is the asset critical? Are existing controls blocking the exploit? Could a threat actor progress beyond initial access?

Figure 1. Deprioritizing Theoretical Vulnerabilities, Focusing on Gaps that Matters

Picus Exposure Validation operationalizes this approach by simulating real-world attack scenarios using Breach and Attack Simulation (BAS) and Automated Penetration Testing, confirming both the exploitability of entry points and how an attacker could move through the environment. This validation feeds into the Picus Exposure Score (PXS), a contextual, evidence-based metric that reflects real risk.

By combining attack surface discovery with exposure validation, organizations avoid wasting resources on theoretical risks and focus remediation on the threats that matter most to their business. Prioritization becomes practical, provable, and aligned with actual adversary behavior.

How Can Organizations Protect Their Attack Surface From Advanced Persistent Threats (APTs)?

Advanced Persistent Threats (APTs) are stealthy, long-term attacks targeting high-value assets. Their success often depends on unnoticed footholds in an organization's attack surface. To protect against APTs, organizations must combine proactive defense, contextual validation, and continuous monitoring:

• Attack Surface Management: Continuously discover and monitor all exposed assets, including cloud services, APIs, and remote access points, to eliminate blind spots APTs may exploit.

• Continuous Security Validation: Use platforms like Picus Exposure Validation to simulate adversary behavior regularly. This helps identify whether exposures are exploitable and whether current defenses are capable of blocking full kill-chain campaigns.

• Real-Time Monitoring: Implement threat detection tools (e.g., IDS, IPS, EDR) and behavioral analytics to detect anomalies early and disrupt attacker persistence.

• Timely Patching: Quickly remediate known vulnerabilities. Combine patching efforts with exposure validation to ensure focus remains on exploitable, not just high-scoring, risks.

• Zero Trust Architecture: Apply least-privilege access policies and verify every user and device before granting access, even within the internal network.

• Security Awareness Training: Educate staff on phishing, social engineering, and safe data handling, as many APTs begin with human error.

• Incident Response Planning: Prepare and test IR plans to contain and investigate intrusions quickly, minimizing lateral movement and data loss.

By layering attack surface visibility, continuous validation, and adaptive monitoring, organizations can reduce exploitable entry points, verify their true risk exposure, and build stronger resilience against persistent, targeted threats.