How an IcedID Loader Attack Unfolds: A Case Study in EDR Evasion
Author
Zeen Rachidi
Date Published
Dr. Srinidhi Varadarajan, Chief Scientist, Elastio
In the relentless fight against ransomware, security teams face the constant challenge of thwarting malicious activities that evade the defenses of Endpoint Detection and Response (EDR) systems. This article delves into EDR evasion, with a particular focus on the IcedID loader—a case study that vividly illustrates the sophisticated tactics employed by cyber criminals.
IcedID Loader: A Case Study in EDR Evasion
IcedID, a loader used by various malware families including Quantum, exemplifies this sophistication. Attackers distribute emails pretending to contain a 'corporate document' often labeled with a familiar name such as 'strategy' and a date stamp – a common practice for versioning documents that doesn’t raise any flags for the recipient. However, the document is a decoy; it's password-protected not for security, but to conceal malware.
The trickery lies in the password's uniqueness; it varies with each email, making the malware-laden document appear different every time. This variability renders signature-based scanning and antivirus (AV) detection ineffective, as the file does not match any known malware signatures.
The Attack Unfolds
Stage 1 – Embedded malware is activated
When the recipient opens the document, they are prompted to enter the password provided in the email. Once entered, the document claims to be from an outdated version of Word and prompts the user to click ‘enable editing’ to see the rest of the document. This is a critical moment as, enabling editing activates macros within the document, initiating the download of the malware's second stage.
Stage 2 – The PNG Deception
For the second stage, IcedID downloads a file, such as a PNG, onto a directory. This PNG image, when opened, is nothing more than a transparent background, but hidden within is a DLL (Dynamic Link Library), a typical Windows library that any dynamically linked applications use. In a process called “steganography,” the loader code extracts what the DLL hidden inside the PNG.
Stage 3 – DLL Injection and Further Infection
The loader exploits a legitimate Windows process, runDLL32, to inject the malicious DLL into the system's memory. It's from this vantage point that the DLL reaches out to the command and control server and downloads the actual malware executable.
In Conclusion
With these multi-step attacks designed specifically to sidestep conventional defenses, the need for constant vigilance and dynamic defensive strategies becomes glaringly evident. Traditional antivirus and EDR solutions are important and essential – but they are not enough to counter these sophisticated threats. The key to staying at least one step ahead of these threat actors and defending your organization in today’s threat landscape requires a strategy that leverages behavioral-based detection and a proactive and adaptable posture.
For more on this topic, check out our webinar – Why XDR is not enough to stop ransomware attacks
Recover With Certainty
See how Elastio validates every backup across clouds and platforms to recover faster, cut downtime by 90%, and achieve 25x ROI.
Related Articles
Cloud ransomware incidents rarely begin with visible disruption. More often, they unfold quietly, long before an alert is triggered or a system fails. By the time incident response teams are engaged, organizations have usually already taken decisive action. Workloads are isolated. Instances are terminated. Cloud dashboards show unusual activity. Executives, legal counsel, and communications teams are already involved. And very quickly, one question dominates every discussion. What can we restore that we actually trust? That question exposes a critical gap in many cloud-native resilience strategies. Most organizations have backups. Many have immutable storage, cross-region replication, and locked vaults. These controls are aligned with cloud provider best practices and availability frameworks. Yet during ransomware recovery, those same organizations often cannot confidently determine which recovery point is clean. Cloud doesn’t remove ransomware risk — it relocates it This is not a failure of effort. It is a consequence of how cloud architectures shift risk. Cloud-native environments have dramatically improved the security posture of compute. Infrastructure is ephemeral. Servers are no longer repaired; they are replaced. Containers and instances are designed to be disposable. From a defensive standpoint, this reduces persistence at the infrastructure layer and limits traditional malware dwell time. However, cloud migration does not remove ransomware risk. It relocates it. Persistent storage remains long-lived, highly automated, and deeply trusted. Object stores, block snapshots, backups, and replicas are designed to survive everything else. Modern ransomware campaigns increasingly target this persistence layer, not the compute that accesses it. Attackers don’t need malware — they need credentials Industry investigations consistently support this pattern. Mandiant, Verizon DBIR, and other threat intelligence sources report that credential compromise and identity abuse are now among the most common initial access vectors in cloud incidents. Once attackers obtain valid credentials, they can operate entirely through native cloud APIs, often without deploying custom malware or triggering endpoint-based detections. From an operational standpoint, these actions appear legitimate. Data is written, versions are created, snapshots are taken, and replication occurs as designed. The cloud platform faithfully records and preserves state, regardless of whether that state is healthy or compromised. This is where many organizations encounter an uncomfortable reality during incident response. Immutability is not integrity Immutability ensures that data cannot be deleted or altered after it is written. It does not validate whether the data was already encrypted, corrupted, or poisoned at the time it was captured. Cloud-native durability and availability controls were never designed to answer the question incident responders care about most: whether stored data can be trusted for recovery. In ransomware cases, incident response teams repeatedly observe the same failure mode. Attackers encrypt or corrupt production data, often gradually, using authorized access. Automated backup systems snapshot that corrupted state. Replication propagates it to secondary regions. Vault locks seal it permanently. The organization has not lost its backups. It has preserved the compromised data exactly as designed. Backup isolation alone is not enough This dynamic is particularly dangerous in cloud environments because it can occur without malware, without infrastructure compromise, and without violating immutability controls. CISA and NIST have both explicitly warned that backup isolation and retention alone are insufficient if integrity is not verified. Availability testing does not guarantee recoverability. Replication can accelerate the blast radius Replication further amplifies the impact. Cross-region architectures prioritize recovery point objectives and automation speed. When data changes in a primary region, those changes are immediately propagated to disaster recovery environments. If the change is ransomware-induced corruption, replication accelerates the blast radius rather than containing it. From the incident response perspective, this creates a critical bottleneck that is often misunderstood. The hardest part of recovery is deciding what to restore The hardest part of recovery is not rebuilding infrastructure. Cloud platforms make redeployment fast and repeatable. Entire environments can be recreated in hours. The hardest part is deciding what to restore. Without integrity validation, teams are forced into manual forensic processes under extreme pressure. Snapshots are mounted one by one. Logs are reviewed. Timelines are debated. Restore attempts become experiments. Every decision carries risk, and every delay compounds business impact. This is why ransomware recovery frequently takes days or weeks even when backups exist. Boards don’t ask “Do we have backups?” Boards do not ask whether backups are available. They ask which recovery point is the last known clean state. Without objective integrity assurance, that question cannot be answered deterministically. This uncertainty is not incidental. It is central to how modern ransomware creates leverage. Attackers understand that corrupting trust in recovery systems can be as effective as destroying systems outright. What incident response teams wish you had is certainty What incident response teams consistently wish organizations had before an incident is not more backups, but more certainty. The ability to prove, not assume, that recovery data is clean. Evidence that restoration decisions are based on validated integrity rather than best guesses made under pressure. Integrity assurance is the missing control This is where integrity assurance becomes the missing control in many cloud strategies. NIST CSF explicitly calls for verification of backup integrity as part of the Recover function. Yet most cloud-native architectures stop at durability and immutability. When integrity validation is in place, recovery changes fundamentally. Organizations can identify the last known clean recovery point ahead of time. Recovery decisions become faster, safer, and defensible. Executive and regulatory confidence improves because actions are supported by evidence. From an incident response standpoint, the difference is stark. One scenario is prolonged uncertainty and escalating risk. The other is controlled, confident recovery. Resilience is proving trust, not storing data Cloud-native architecture is powerful, but ransomware has adapted to it. In today’s threat landscape, resilience is no longer defined by whether data exists somewhere in the cloud. It is defined by whether an organization can prove that the data it restores is trustworthy. That is what incident response teams see after cloud ransomware. Not missing backups, but missing certainty. Certainty is the foundation of recovery And in modern cloud environments, certainty is the foundation of recovery.
CMORG’s Data Vaulting Guidance: Integrity Validation Is Now a Core Requirement In January 2025, the Cross Market Operational Resilience Group (CMORG) published Cloud-Hosted Data Vaulting: Good Practice Guidance. It is a timely and important contribution to the operational resilience of the UK financial sector. CMORG deserves recognition for treating recovery architecture as a priority, not a future initiative. In financial services, the consequences of a cyber event extend well beyond a single institution. When critical systems are disrupted and recovery fails, the impact can cascade across customers, counterparties, and markets. The broader issue is confidence. A high-profile failure to recover can create damage that reaches far beyond the affected firm. This is why CMORG’s cross-industry collaboration matters. It reflects an understanding that resilience is a shared responsibility. Important Theme: Integrity Validation The guidance does a strong job outlining the principles of cloud-hosted vaulting, including isolation, immutability, access control, and key management. These are necessary design elements for protecting recovery data against compromise. But a highly significant element of the document is its emphasis on integrity validation as a core requirement. CMORG Foundation Principle #11 states: “The data vault solution must have the ability to run analytics against its objects to check integrity and for any anomalies without executing the object. Integrity checks must be done prior to securing the data, doing it post will not ensure recovery of the original data or the service that the data supported.” This is a critical point. Immutability can prevent changes after data is stored, but it cannot ensure that the data was clean and recoverable at the time it was vaulted. If compromised data is written into an immutable environment, it becomes a permanently protected failure point. Integrity validation must occur before data becomes the organization’s final recovery source of truth. CMORG Directly Addresses the Risk of Vaulting Corrupted Data CMORG reinforces this reality in Annex A, Use Case #2, which addresses data corruption events: “For this use case when data is ‘damaged’ or has been manipulated having the data vaulted would not help, since the vaulted data would have backed up the ‘damaged’ data. This is where one would need error detection and data integrity checks either via the application or via the backup product.” This is one of the most important observations in the document. Vaulting can provide secure retention and isolation, but it cannot determine whether the data entering the vault is trustworthy. Without integrity controls, vaulting can unintentionally preserve compromised recovery points. The Threat Model Has Changed The guidance aligns with what many organizations are experiencing in practice. Cyber-attacks are no longer limited to fast encryption events. Attackers increasingly focus on compromising recovery, degrading integrity over time, and targeting backups and recovery infrastructure. These attacks may involve selective encryption, gradual corruption, manipulation of critical datasets, or compromise of backup management systems prior to detonation. In many cases, the goal is to eliminate confidence in restoration and increase leverage during extortion. The longer these attacks go undetected, the more likely compromised data is replicated across snapshots, backups, vaults, and long-term retention copies. At that point, recovery becomes uncertain and time-consuming, even if recovery infrastructure remains available. Why Integrity Scanning Must Happen Before Data Is Secured CMORG’s point about validating integrity before data is secured is particularly important. Detection timing directly affects recovery outcomes. Early detection preserves clean recovery points and reduces the scope of failed recovery points. Late detection increases the likelihood that all available recovery copies contain the same corruption or compromise. This is why Elastio’s approach is focused on integrity validation of data before it becomes the foundation of recovery. Organizations need a way to identify ransomware encryption patterns and corruption within data early for recovery to be predictable and defensible. A Meaningful Step Forward for the Industry CMORG’s cloud-hosted data vaulting guidance represents an important milestone. It reflects a mature view of resilience that recognizes vaulting and immutability as foundational, but incomplete without integrity validation. The integrity of data must be treated as a primary control. CMORG is correct to call this out. It is one of the clearest statements published by an industry body on what effective cyber vaulting must include to support real recovery.
Closing the Data Integrity Control Gap In 2025, the cybersecurity narrative shifted from protection to provable resilience. The reason? A staggering 333% surge in "Hunter-Killer" malware threats designed not just to evade your security stack, but to systematically dismantle it. For CISOs and CTOs in regulated industries, this isn't just a technical hurdle; it is a Material Risk that traditional recovery frameworks are failing to address. The Hunter-Killer Era: Blinding the Frontline The Picus Red Report 2024 identified that one out of every four malware samples now includes "Hunter-Killer" functionality. These tools, like EDRKillShifter, target the kernel-level "callbacks" that EDR and Antivirus rely on to monitor your environment. The Result: Your dashboard shows a "Green" status, while the adversary is silently corrupting your production data. This creates a Recovery Blind Spot that traditional, agent-based controls cannot see. The Material Impact: Unquantifiable Downtime When your primary defense is blinded, the "dwell time", the period an attacker sits in your network, balloons to a median of 11–26 days. In a regulated environment, this dwell time is a liability engine: The Poisoned Backup: Ransomware dwells long enough to be replicated into your "immutable" vaults.The Forensic Gridlock: Organizations spend an average of 24 days in downtime manually hunting for a "clean" recovery point.The Disclosure Clock: Under current SEC mandates, you have four days to determine the materiality of an incident. If you can’t prove your data integrity, you can’t accurately disclose your risk. Agentless Sovereignty: The Missing Control Elastio addresses the Data Integrity Gap by sitting outside the line of fire. By moving the validation layer from the compromised OS to the storage layer, we provide the only independent source of truth. The Control GapThe Elastio OutcomeAgent FragilityAgentless Sovereignty: Sitting out-of-band, Elastio is invisible to kernel-level "Hunter-Killer" malware.Trust BlindnessIndependent Truth: We validate data integrity directly from storage, ensuring recovery points are clean before you restore.Forensic LagMean Time to Clean Recovery (MTCR): Pinpoint the exact second of integrity loss to slash downtime from weeks to minutes. References & Sources GuidePoint Security GRIT 2026 Report: 58% year-over-year increase in ransomware victims.Picus Security Red Report 2024: 333% surge in Hunter-Killer malware targeting defensive systems.ESET Research - EDRKillShifter Analysis: Technical deep-dive into RansomHub’s custom EDR killer and BYOVD tactics.Mandiant M-Trends 2025: Median dwell time increases to 11 days; 57% of breaches notified by external sources.Pure Storage/Halcyon/RansomwareHelp: Average ransomware downtime recorded at 24 days across multiple industries in 2025.Cybereason True Cost to Business: 80% of organizations who pay a ransom are hit a second time.