Global malware activity climbed sharply over the past week, with remote access trojans (RATs), information stealers, and loaders all posting significant week-over-week gains, according to threat sample uploads tracked by ANY.RUN.

AsyncRAT topped the chart with 211 uploads, edging out Remcos at 196 and Xworm at 183. This trend signals that RAT-based intrusions remain the dominant tactic for cybercriminals seeking persistent, hands-on-keyboard access to compromised Windows systems.

AsyncRAT held the number one position with 211 total uploads and a modest weekly increase of two samples, reflecting its status as one of the most consistently deployed .NET-based remote access trojans in the current threat landscape. The malware is typically delivered through phishing email attacks containing malicious attachments or links.

Once installed, it grants attackers full remote command execution, keylogging, screen capture, and data exfiltration capabilities.

Recent campaigns have shown AsyncRAT operators abusing trusted cloud infrastructure such as Cloudflare’s free-tier services and TryCloudflare tunnels to host payload delivery servers, making detection significantly harder for conventional security tools.

Top 10 Malware Threats of the Week

Remcos RAT recorded the largest single gain among the top three, rising by 59 samples to reach 196 total uploads, underscoring an intensifying wave of espionage and surveillance-driven campaigns.

Originally marketed as a legitimate remote administration tool, Remcos has evolved into a favored espionage and credential-theft platform for both cybercriminals and initial access brokers.

Newer variants observed in early 2026 have shifted toward real-time surveillance, streaming live webcam footage and transmitting keystrokes instantly rather than waiting to exfiltrate stored data, effectively turning infected machines into live monitoring feeds for attackers.

Xworm followed closely with 183 uploads and a gain of 16, continuing its reputation as a highly adaptable, modular RAT sold through malware-as-a-service channels.

Recent Xworm campaigns have leveraged multiple file formats and scripting languages, including PowerShell, VBS, HTA, and Office macro exploits such as CVE-2018-0802, to stage payloads and evade endpoint defenses.

Beyond typical RAT functions like keylogging and webcam access, newer Xworm builds also incorporate destructive capabilities to deploy stealthy infostealer payloads, file encryption, and distributed denial-of-service (DDoS) features.

AgentTesla ranked fourth with 172 uploads and a sharp 51-sample increase, reaffirming its long-standing role as one of the most prolific credential-stealing Trojans in circulation.

Close behind, Stealc posted the single largest weekly jump of the entire list, up 67 samples to reach 159 total uploads, followed by Vidar at 157 with a smaller rise of six.

Both are widely used information stealers designed to harvest browser credentials, cryptocurrency wallet data, and session tokens from infected endpoints.

As detailed in the weekly threat metrics published in the ANY.RUN malware analysis, DonutLoader climbed 16 samples to 140 uploads, reflecting its growing role as a delivery mechanism for secondary payloads, while Lumma stealer rose 27 samples to 126. Formbook rounded out the mid-tier with 97 uploads, up 21 for the week.

Snake was the only family among the top ten to decline, dropping two samples to close the week at 93 total uploads, a modest but notable exception amid an otherwise broad surge across nearly every major malware category.

Security teams are advised to prioritize detection rules for phishing-based delivery chains, monitor for anomalous PowerShell and HTA execution, and flag traffic to known Remcos, AsyncRAT, and Xworm command-and-control infrastructure to blunt the impact of this activity spike.

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A newly demonstrated technique shows how malware in a compromised Windows user session can abuse Windows Hello for Business (WHFB) cryptographic keys to authenticate to Microsoft Entra ID, enabling attackers to gain cloud access without the victim’s password, PIN, or biometric data.

Windows Hello for Business is designed as a passwordless authentication system. It normally stores a user’s private key in the device’s Trusted Platform Module, or TPM, making the key difficult to export or steal. Users unlock access to that key with a PIN, fingerprint, facial recognition, or another local verification method.

However, researcher Dirk-jan Mollema found that a process already operating within an active user session may be able to use the key through Windows cryptographic interfaces without triggering a fresh PIN or biometric prompt. This behavior appears linked to cached authentication information used by Windows Hello.

The issue does not mean that attackers can simply copy a TPM-protected private key from a device. Instead, malware with access to an unlocked user session could ask Windows to perform cryptographic signing operations using the protected key. Those signatures can then be used in identity flows that prove control of the Windows Hello credential.

Windows Hello Key Abuse Targets Entra ID

One attack path involves requesting a Primary Refresh Token, also known as a PRT. PRTs are important Microsoft Entra ID authentication artifacts that support single sign-on across Microsoft services and applications.

A valid PRT can provide long-lived access and may be renewed, making it highly valuable to attackers seeking persistence in a cloud environment.

Previously, an attacker would also need access to another Entra ID-joined or registered device to complete this flow. The new research shows a second option: treating the Windows Hello for Business key as a FIDO2 passkey through the WebAuthn authentication protocol.

WebAuthn is widely used for passwordless authentication and phishing-resistant sign-in. By generating a valid WebAuthn assertion with the victim’s Windows Hello key, an attacker could authenticate to Microsoft Entra ID from a separate machine.

The resulting access tokens may lack a device identifier because the sign-in does not include the victim device’s normal registration state.

That missing device identifier can be useful to an attacker. Tokens without device-bound state may be used to register a new attacker-controlled device in Entra ID.

From there, an attacker could attempt to obtain a PRT, establish persistence, or add new authentication methods such as passkeys. The research also highlights a challenge for Conditional Access policies.

Because Windows Hello and FIDO2 are considered phishing-resistant authentication methods, a forged authentication flow based on a compromised session may satisfy policies requiring strong multifactor authentication.

Policies that require compliant or managed devices could still block some activity, but attackers may attempt to work around device restrictions after gaining cloud access.

Defenders should monitor Entra ID sign-in logs for Windows Hello for Business authentications where the device ID is empty. While this can occur legitimately in private browsing sessions or browsers without single sign-on support, it should be relatively uncommon in many enterprise environments.

Organizations should also investigate unexpected device registrations, newly added authentication methods, unusual token activity, and sign-ins that follow endpoint compromise. Protecting active Windows sessions remains essential, because the attack relies on malware already running as the targeted user.

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