Query: indicators of IIS Components
Matching passage: T1505.004 IIS Components. Tactics: persistence. Description: Adversaries may install malicious components that run on Internet Information Services (IIS) web servers to establish persistence. IIS provides several mechanisms to extend the functionality of the web servers. For example, Internet Server Application Programming Interface (ISAPI) extensions and filters can be installed to examine and/or modify incoming and outgoing IIS web requests. Extensions and filters are deployed as DLL files that export three functions: <code>Get{Extension/Filter}Version</code>, <code>Http{Extension/Filter}Proc</code>, and (optionally) <code>Terminate{Extension/Filter}</code>. IIS modules may also be installed to extend IIS web servers.(Citation: Microsoft ISAPI Extension Overview 2017)(Citation: Microsoft ISAPI Filter Overview 2017)(Citation: IIS Backdoor 2011)(Citation: Trustwave IIS Module 2013) Adversaries may install malicious ISAPI extensions and filters to observe and/or modify traffic, execute commands on compromised machines, or proxy command and control traffic. ISAPI extensions and filters may have access to all IIS web requests and responses. For example, an adversary may abuse these mechanisms to modify HTTP responses in order to distribute malicious commands/content to previously comprised hosts.(Citation: Microsoft ISAPI Filter Overview 2017)(Citation: Microsoft ISAPI Extension Overview 2017)(Citation: Microsoft ISAPI Extension All Incoming 2017)(Citation: Dell TG-3390)(Citation: Trustwave IIS Module 2013)(Citation: MMPC ISAPI Filter 2012) Adversaries may also install malicious IIS modules to observe and/or modify traffic. IIS 7.0 introduced modules that provide the same unrestricted access to HTTP requests and responses as ISAPI extensions and filters. IIS modules can be written as a DLL that exports <code>RegisterModule</code>, or as a .NET application that interfaces with ASP.NET APIs to access IIS HTTP requests.(Citation: Microsoft IIS Modules Overview 2007)(Citation: Trustwave IIS Module 2013)(Citation: ESET IIS Malware 20
Near-miss passage: T1505.006 vSphere Installation Bundles. Tactics: persistence. Description: Adversaries may abuse vSphere Installation Bundles (VIBs) to establish persistent access to ESXi hypervisors. VIBs are collections of files used for software distribution and virtual system management in VMware environments. Since ESXi uses an in-memory filesystem where changes made to most files are stored in RAM rather than in persistent storage, these modifications are lost after a reboot. However, VIBs can be used to create startup tasks, apply custom firewall rules, or deploy binaries that persist across reboots. Typically, administrators use VIBs for updates and system maintenance. VIBs can be broken down into three components:(Citation: VMware VIBs) * VIB payload: a `.vgz` archive containing the directories and files to be created and executed on boot when the VIBs are loaded. * Signature file: verifies the host acceptance level of a VIB, indicating what testing and validation has been done by VMware or its partners before publication of a VIB. By default, ESXi hosts require a minimum acceptance level of PartnerSupported for VIB installation, meaning the VIB is published by a trusted VMware partner. However, privileged users can change the default acceptance level using the `esxcli` command line interface. Additionally, VIBs are able to be installed regardless of acceptance level by using the <code> esxcli software vib install --force</code> command. * XML descriptor file: a configuration file containing associated VIB metadata, such as the name of the VIB and its dependencies. Adversaries may leverage malicious VIB packages to maintain persistent access to ESXi hypervisors, allowing system changes to be executed upon each bootup of ESXi – such as using `esxcli` to enable firewall rules for backdoor traffic, creating listeners on hard coded ports, and executing backdoors.(Citation: Google Cloud Threat Intelligence ESXi VIBs 2022) Adversaries may also masquerade their malicious VIB files as PartnerSupported by modifying the XML descriptor file.(Citation: Googl