Query: EDR alert: possible Downgrade Attack (T1689)
Matching passage: T1689 Downgrade Attack. Tactics: defense impairment. Description: Adversaries may downgrade or use a version of system features that may be outdated, vulnerable, and/or does not support updated security controls. Downgrade attacks typically take advantage of a system’s backward compatibility to force it into less secure modes of operation. Adversaries may downgrade and use various less-secure versions of features of a system, such as [Command and Scripting Interpreter](https://attack.mitre.org/techniques/T1059) or even network protocols that can be abused to enable [Adversary-in-the-Middle](https://attack.mitre.org/techniques/T1557) or [Network Sniffing](https://attack.mitre.org/techniques/T1040).(Citation: Praetorian TLS Downgrade Attack 2014) For example, [PowerShell](https://attack.mitre.org/techniques/T1059/001) versions 5+ includes Script Block Logging (SBL), which can record executed script content. However, adversaries may attempt to execute a previous version of PowerShell that does not support SBL with the intent to impair defenses while running malicious scripts that may have otherwise been detected.(Citation: CrowdStrike downgrade attack)(Citation: Google Cloud downgrade attack)(Citation: att_def_ps_logging) Adversaries may similarly target network traffic to downgrade from an encrypted HTTPS connection to an unsecured HTTP connection that exposes network data in clear text.(Citation: Targeted SSL Stripping Attacks Are Real)(Citation: CrowdStrike Downgrade attack 2) On Windows systems, adversaries may downgrade the boot manager to a vulnerable version that bypasses Secure Boot, granting the ability to disable various operating system security mechanisms.(Citation: SafeBreach)
Near-miss passage: T1553.001 Gatekeeper Bypass. Tactics: defense impairment. Description: Adversaries may modify file attributes and subvert Gatekeeper functionality to evade user prompts and execute untrusted programs. Gatekeeper is a set of technologies that act as layer of Apple’s security model to ensure only trusted applications are executed on a host. Gatekeeper was built on top of File Quarantine in Snow Leopard (10.6, 2009) and has grown to include Code Signing, security policy compliance, Notarization, and more. Gatekeeper also treats applications running for the first time differently than reopened applications.(Citation: TheEclecticLightCompany Quarantine and the flag)(Citation: TheEclecticLightCompany apple notarization ) Based on an opt-in system, when files are downloaded an extended attribute (xattr) called `com.apple.quarantine` (also known as a quarantine flag) can be set on the file by the application performing the download. Launch Services opens the application in a suspended state. For first run applications with the quarantine flag set, Gatekeeper executes the following functions: 1. Checks extended attribute – Gatekeeper checks for the quarantine flag, then provides an alert prompt to the user to allow or deny execution.(Citation: OceanLotus for OS X)(Citation: 20 macOS Common Tools and Techniques) 2. Checks System Policies - Gatekeeper checks the system security policy, allowing execution of apps downloaded from either just the App Store or the App Store and identified developers. 3. Code Signing – Gatekeeper checks for a valid code signature from an Apple Developer ID. 4. Notarization - Using the `api.apple-cloudkit.com` API, Gatekeeper reaches out to Apple servers to verify or pull down the notarization ticket and ensure the ticket is not revoked. Users can override notarization, which will result in a prompt of executing an “unauthorized app” and the security policy will be modified. Adversaries can subvert one or multiple security controls within Gatekeeper checks through logic errors (e.g. [Exploitation for Stealth](https://a