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PoisonedRefresh: A Fileless Linux Rootkit That Injects PHP Web Shells Into F5 BIG-IP APM Server Memory

Sophos details PoisonedRefresh, a fileless Linux rootkit that injects a memory-resident PHP web shell into F5 BIG-IP APM after exploitation of CVE-2025-53521.

On September 8, 2026, SophosLabs published an analysis of Linux/Agnt-IC (dubbed PoisonedRefresh by ESET) found in compromised F5 BIG-IP Access Policy Manager environments. Initial access leverages CVE-2025-53521, an unauthenticated RCE in BIG-IP APM when an access policy is configured on a virtual server; F5 confirmed exploitation and links the activity to cluster c05d5254, while Shadowserver observed 795 exposed vulnerable endpoints. A first stage hidden in a modified umount binary modifies /usr/sbin/httpd and SELinux configuration and embeds itself in BIG-IP upgrade images for persistence. The second-stage ELF intercepts __libc_start_main, hooks apr_dso_load, and injects a PHP web shell into libphp memory via mmap manipulation, leaving no disk artifacts, and exposes a /bin/bash shell via a local UNIX domain socket instead of a TCP port.

Security Affairs · 8d agoMalware in the wildCVE-2025-53521

Hackers breach F5 BIG-IP APM devices to deploy Linux rootkit

Sophos analyzed a Linux rootkit on F5 BIG-IP APM devices that injects a fileless PHP web shell, likely after CVE-2025-53521 exploitation.

Sophos analyzed a Linux rootkit targeting F5 BIG-IP APM environments, also tracked by ESET as PoisonedRefresh, which hijacks Apache's apr_dso_load module loader to inject a fileless PHP web shell into memory. The implant intercepts __libc_start_main, hides strings with RC4, creates a password-protected local UNIX socket backdoor for interactive Bash access, and persists across BIG-IP upgrade images while modifying SELinux configuration. It is likely a second-stage payload following exploitation of CVE-2025-53521, a critical RCE flaw F5 reclassified from a DoS issue in March. The ShadowServer Foundation tracked 795 F5 BIG-IP APM endpoints exposed online.

BleepingComputer · 8d agoMalware in the wildCVE-2025-53521

RatHat Abuses Android Wireless Debugging to Gain Shell Access and Steal Banking PINs

New Android banking trojan RatHat abuses Wireless Debugging to gain shell access and steals banking PINs and OTPs via raw touch capture.

Zimperium and zLabs analyzed RatHat, an Android banking malware linked to China-based actors that chains Accessibility abuse and Wireless Debugging to obtain a local ADB shell without a host computer. Masqueraded Go binaries in /data/local/tmp provide persistence and an FRP reverse tunnel, while a getevent-based collector maps touch coordinates to PIN pads and pattern locks using locateValues.json layouts. It targets banking, crypto, WeChat and Alipay apps through smishing, malicious ads, and HTML overlays, and serializes the accessibility tree for a generative AI assistant to automate on-screen actions. Layered anti-analysis includes malformed DEX, a padded manifest, and debugger, Frida, and emulator checks.

GBHackersupdated · 53m agofirst · 1h agoMalware in the wild 2 sources

KREMLIN Banking Malware Bypasses Chrome Security to Steal Banking Sessions

Elastic Security Labs details KREMLIN, a Brazilian banking malware that implants malicious Chrome and Edge extensions by forging Chromium integrity values to steal banking sessions.

Elastic Security Labs tracks the KREMLIN banking malware operation as REF9334, active since at least May 2025 across seven campaigns primarily targeting 12 Brazilian banks. The malware is installed by a victim-run JavaScript loader, achieves scheduled-task persistence, and side-loads a malicious DLL via SentinelOne's SentinelMemoryScanner.exe. It modifies Chrome and Edge Secure Preferences files, enables developer mode, and regenerates Chromium MAC values to silently install extensions, while extracting browser encryption material including the newer App-Bound OSCrypt key. An Ethereum smart contract serves as a dead-drop resolver for C2 config; Elastic disrupted over 1,500 infections via a canary domain.

GBHackers · 1d agoMalware in the wild 2 sources

Stealth rootkit targeting F5 BIG-IP could expose enterprise identity gateways

Sophos analyzed a stealth Linux rootkit that hides a web shell in memory on compromised F5 BIG-IP APM identity gateways, evading file-based detection.

Sophos analyzed a second-stage Linux rootkit implant found in compromised F5 BIG-IP APM environments running Apache and PHP, linked to exploitation of CVE-2025-53521, an unauthenticated RCE. The implant hooks Apache's PHP-loading process and serves modified in-memory versions of three legitimate webtop PHP files (apm_css.php3, full_wt.php3, webtop_popup_css.php3), leaving on-disk files untouched so hashes and integrity checks pass. It also establishes access via an authenticated local UNIX socket that can provide an interactive /bin/bash session. Experts warn compromised APM appliances, which handle federated SSO and terminate TLS at enterprise perimeters, could enable SSO token theft and lateral movement to trusted downstream applications.

CSO Online · 6d agoMalware in the wildCVE-2025-53521

Hackers deploy Linux rootkit on F5 BIG-IP APM devices, hiding web shell in memory

Sophos analyzed a Linux rootkit, tracked as PoisonedRefresh, on hacked F5 BIG-IP APM devices hiding an in-memory web shell linked to exploited CVE-2025-53521.

Sophos and ESET analyzed an implant (named PoisonedRefresh by ESET) deployed on compromised F5 BIG-IP APM appliances, which serves enterprise, financial, government, and public sector deployments. The second-stage payload intercepts __libc_start_main, hooks Apache's APR module loader (apr_dso_load), RC4-encodes key strings, and rewrites PHP file reads in memory to embed a web shell inside legitimate scripts like apm_css.php3, full_wt.php3, and webtop_popup_css.php3, leaving on-disk files unchanged. A related installer component infects /usr/sbin/httpd, persists across BIG-IP upgrade images, modifies SELinux configuration, and deploys the payload. The malware also creates a Unix domain socket at /run/bigtlog.pipe that hands authenticated local connections to /bin/bash; F5 links the activity to CVE-2025-53521, an unauthenticated RCE in BIG-IP APM already exploited in the wild.

Help Net Security · 7d agoMalware in the wildCVE-2025-535211

Manic Android Malware Exfiltrates Data From Offline Phones via Nearby Infected Devices

ThreatFabric identified Manic, an Android banking malware and spyware targeting Ukrainian and European financial apps with novel offline Wi-Fi mesh data exfiltration via nearby infected devices.

ThreatFabric reported a new Android malware family called Manic combining banking fraud and surveillance capabilities, targeting 169 package IDs across Ukrainian banks, government and identity services, messaging apps, and Russian and European financial institutions. The malware uses phishing sites and dropper apps impersonating utilities for distribution and relies on accessibility services and notification permissions for keylogging, overlays, and remote control. It introduces a store-and-forward relay mechanism that stages encrypted data locally and relays it through nearby infected devices via Wi-Fi Direct, Bluetooth RFCOMM, or BLE GATT, supporting up to four hops when the primary device lacks internet access. Activity dates back to February 2026, with active development through late July.

The Hacker News · 26d agoMalware in the wild

Malware bypasses browser checks to force install Chrome, Edge extensions

Elastic Security Labs detailed KREMLIN, a Brazilian banking malware that silently installs malicious Chrome and Edge extensions, with 1,515 confirmed infections.

Elastic Security Labs analyzed KREMLIN, a toolkit used by a Brazilian operation in at least seven campaigns since May 2025 that impersonates 12 banks to trick users into opening a JavaScript file disguised as a bank receipt or invoice. After anti-sandbox checks, it downloads Node.js, persists via a scheduled task, and fetches payload locations from an Ethereum smart contract, hiding payloads in JPEG images on Internet Archive. The toolkit bypasses Chromium integrity mechanisms to install unapproved Chrome/Edge extensions masquerading as AVSync that steal cookies, keylog form input, capture screenshots, and intercept HTTP traffic, while recent campaigns deployed the REMCOS RAT and earlier ones Pulsar RAT. Elastic confirmed 1,515 infected systems, almost all in Brazil, and disrupted the campaign by registering an anti-sandbox canary domain; the linked wallet handled roughly 20,800 USDT incoming and 19,000 USDT outgoing.

BleepingComputer · 14h agoMalware in the wild 3 sources

ToxicPanda 2.0 and GoldDigger Expand Android Banking Attacks with On

Zimperium and IBM Trusteer report expanded ToxicPanda 2.0 and GoldDigger Android banking trojan campaigns now targeting 349 financial institutions across 16 countries.

Zimperium zLabs reports ToxicPanda 2.0 (TgToxic) now carries 167 remote commands, targets 349 financial institutions across 16 countries via more than 140 banking and cryptocurrency apps, and abuses Android Wireless Debugging via ADB for privilege escalation and shell access. It harvests lock screen PINs with fake overlays, steals UI elements via accessibility services, sets Device Administrator privileges, and is distributed through Amazon AWS-hosted buckets. IBM Trusteer documents a GoldDigger campaign impersonating airline companies and shopping retailers, causing massive infections in South Africa and the U.K., obfuscated with the dpt-shell packer that detects Frida and resists debugging. GoldDigger performs on-device fraud by injecting input into banking apps and is attributed to the Chinese-speaking GoldFactory actor.

The Hacker News · 24d agoMalware in the wild

Manic: The Android Malware That Exfiltrates Data Even When the Phone Is Offline

ThreatFabric identifies Manic, an Android banking fraud and spyware platform targeting Ukraine with offline Bluetooth/Wi-Fi Direct mesh exfiltration and device takeover.

ThreatFabric's Mobile Threat Intelligence team identified Manic, an Android malware active in the wild since at least February 2026 that combines banking fraud with surveillance and device-control capabilities. It monitors 169 Android apps including Ukrainian banks, government and eID services, messaging apps, crypto exchanges, and 2FA tools, using the Accessibility service as a classified UI keylogger and WebRTC for live screen viewing and remote control. A distinctive store-and-forward relay exfiltrates AES-GCM-encrypted data through nearby infected devices over Wi-Fi Direct, Bluetooth RFCOMM, or BLE GATT, supporting chains of up to four hops when direct C2 is unavailable. A July update added stronger anti-analysis, in-memory DEX loading, lock-secret phishing to extract device PINs, and hiding from the app launcher.

Security Affairs · 27d agoMalware in the wild

737 Chrome VPN Extensions Caught Routing Traffic Through Proxies. Check If You Have One

Researchers found 737 Chrome VPN extensions, many impersonating brands like NordVPN, routing roughly 75,000 users' browser traffic through attacker-controlled SOCKS5 proxies.

Socket and researcher Kush Pandya identified 737 Chrome VPN and proxy extensions, published across at least 40 developer accounts with 75,486 installs, that route entire browser sessions through one provider's SOCKS5 proxies on port 1082. Of these, 274 impersonate 66 established brands including Proton VPN, NordVPN, Surfshark, ExpressVPN, and Cloudflare 1.1.1.1. The proxy bypass list only excludes loopback addresses, exposing visited destinations, source IPs, TLS SNI values, and plain-HTTP request bodies to the operator. 221 extensions have been removed from the Chrome Web Store while 516 remain listed as active.

The Hacker News · Aug 12, 2026Malware