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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.
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Understanding Angler Exploit Kit
Unit 42 examines Angler EK operations, including rapid zero-day adoption, fileless Bedep infections, and ransomware payloads like TeslaCrypt and CryptXXX.
Unit 42 published the second part of its Angler EK analysis, covering the kit's history since 2013, its SaaS rental model, and its focus on Flash, Internet Explorer, and Silverlight exploits. Angler integrated the CVE-2015-5119 Flash zero-day from the Hacking Team leak within hours and later added exploits for CVE-2015-2419 and CVE-2016-0034 roughly a month after Microsoft patched them. Campaigns use Angler to deliver ransomware such as CryptoWall, TeslaCrypt, and CryptXXX, plus banking trojans and stealers via EITest. Since August 2014, Angler has used fileless, in-memory execution, most often for Bedep, which later downloads CryptXXX and click-fraud malware.
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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.
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ClearFake WebDAV infection chain delivers Amatera stealer, ZigCryptoStealer, and NetSupport Manager
Cisco Talos details ClearFake WebDAV chains delivering Amatera stealer to a Ukrainian government organization, with cryptocurrency and credential theft payloads.
Cisco Talos investigated DLL executions named 'verification.google' via WebDAV UNC paths at a Ukrainian government organization, tracking the actor as UAT-10820 and assessing with moderate confidence the activity is Russian and opportunistic rather than targeted. The infection chain uses ClearFake JavaScript injected via a Cloudflare Worker, EtherHiding storage on BNB Smart Chain contracts, and a ClickFix fake Google CAPTCHA prompt to deliver Amatera stealer. Secondary payloads differ by C2: one loader deploys ZigCryptoStealer with a Go reverse TCP proxy and a vulnerable driver that kills EDR, while the other installs an unauthorized NetSupport Manager with a Russia-based C2. Similar Amatera chains were separately documented by Malwarebytes and Blackpoint Cyber, but with no shared infrastructure.
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IT threat evolution Q2 2022
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Hackers Disable Endpoint Protection and Deploy Sliver Across Compromised Windows Domain
The Hunter's Ledger tracked campaign UTA-2026-024 using Sliver C2, Domain Admin account creation, and Ethereum-based C2 rotation to compromise a US organization's Windows domain.
The Hunter's Ledger tracked an intrusion at one unnamed US organization as UTA-2026-024, staged from exposed server 193.233.202.17 with a Sliver beacon. Operators created a non-expiring Domain Admin account, enabled RDP with NLA disabled, dumped SAM, SYSTEM and SECURITY hives plus LSASS memory, and disabled eight endpoint protection services. A Node.js implant resolved its C2 server from an Ethereum smart contract that rotated domains five times in five months, while SYSTEM scheduled tasks with backdated dates and DNS allowlist manipulation provided persistence. The infrastructure ties to a confirmed ransomware incident, but no encryptor deployment was proven in this intrusion.
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⚡ Weekly Recap: Chrome 0-Day, AI Hacking Tools, DDR5 Bit
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Hackers Use Cross-Platform Noodle RAT to Secretly Control Windows and Linux Systems
Check Point identifies Noodle RAT as a distinct cross-platform Windows/Linux backdoor used by Chinese-speaking actors against Asia-Pacific organizations since 2016.
Check Point assesses Noodle RAT, also known as ANGRYREBEL, as a distinct backdoor family rather than a variant of Gh0st RAT or Rekoobe, with separate Windows (Win.NOODLERAT) and Linux (Linux.NOODLERAT) variants sharing a common command-and-control design. The Windows implant runs filelessly via shellcode with loaders like MULTIDROP and MICROLOAD, while the Linux variant provides reverse shells, file management, and SOCKS tunneling after exploitation or web-shell placement on exposed servers. Groups including Iron Tiger, Calypso APT, Rocke, and Cloud Snooper have deployed it against organizations in Thailand, India, Japan, Malaysia, and Taiwan. Check Point released sample hashes and C2 IP indicators alongside the analysis.
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Weekly Cybersecurity Newsletter – Top 50 Biggest Cybersecurity Stories of the Week
GBHackers weekly digest rounds up 50 stories including Microsoft's 973-CVE patch drop, exploited Cisco FMC flaws, and Claude agent attacks.
GBHackers' September 7-12, 2026 newsletter summarizes the 50 biggest cybersecurity stories of the week. Highlights include Microsoft patching a record 973 CVEs with two exploited zero-days, active exploitation of Cisco FMC, Check Point VPN and Ivanti flaws, China-linked crews chaining Chrome and Windows zero-days, AI agents mass-exploiting PaperCut to compromise 440 servers, and the emergence of Panzer cross-platform ransomware. It also covers Anthropic and OpenAI agentic AI incidents and CrowdStrike's SafeMind launch.
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Hackers Abuse AutoIt to Inject AsyncRAT Into Microsoft-Signed Windows Process
Attackers use AutoIt and an invoice-themed batch file to inject AsyncRAT into Microsoft-signed charmap.exe for stealthy remote access.
Point Wild Threat Intelligence documented a five-stage campaign starting with 'Right-click to open Invoice Details.bat' that launches hidden PowerShell, drops a renamed AutoIt interpreter and encrypted loader into a random Temp folder, and persists via a Startup-folder batch file. The loader decrypts AsyncRAT only in memory and injects it into the Microsoft-signed charmap.exe (Windows Character Map) process, leaving no payload file on disk. The final payload patches AMSI inside the infected process and includes screen-capture code that prepares images for transfer to a command-and-control server at 158[.]51[.]122[.]136:4944.
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Security Affairs newsletter Round 594 by Pierluigi Paganini – INTERNATIONAL EDITION
Weekly Security Affairs newsletter aggregates top stories including Cisco FMC exploitation, Qilin ransomware, Chrome zero-days, and Berlin leak.
Pierluigi Paganini's Security Affairs newsletter Round 594 (International Edition) rounds up the week's security headlines. Topics include attackers exploiting a critical Cisco FMC flaw to deploy Qilin ransomware, SonicWall mass exploitation linked to a UK council attack, multiple CISA KEV additions, Chrome zero-days used by four nation-state actors, a $320 million Liquid Network theft, and a Berlin ransomware data leak. It also covers AI security items such as agent sandbox failures and distillation campaigns by Chinese AI firms.
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Afraidgate: Major Exploit Kit Campaign Swaps Locky Ransomware for CryptXXX
Unit 42 reports the Afraidgate campaign switched from Nuclear EK delivering Locky to Angler EK delivering CryptXXX via the Bedep downloader.
Unit 42 reported that the Afraidgate campaign, which uses gates registered through FreeDNS at afraid.org, switched in mid-April 2016 from Nuclear EK distributing Locky ransomware to Angler EK distributing CryptXXX. The Angler/Bedep/CryptXXX combination also spread from the pseudo-Darkleech campaign, with Bedep acting as a fileless, memory-resident downloader that also installs click-fraud malware. Recent Bedep updates detect virtual machines and alter behavior, complicating analyst investigation. Unit 42 published gate, EK, and post-infection indicators including gate IP 185.118.164.42 and associated domains.
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Hackers Exploit SharePoint Zero-Day Since July 7 to Steal Keys, Maintain Persistent Access
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