# T1056.003_web-portal-capture

> Adversaries may install code on externally facing portals, such as a VPN login page, to capture and transmit credentials of users who attempt to log into the service.

- Skill: `cyberstrikeus/t1056-003-web-portal-capture` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/t1056-003-web-portal-capture`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/t1056-003-web-portal-capture/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/t1056-003-web-portal-capture

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# T1056.003 Web Portal Capture

> **Sub-technique of:** T1056

## High-Level Description

Adversaries may install code on externally facing portals, such as a VPN login page, to capture and transmit credentials of users who attempt to log into the service. For example, a compromised login page may log provided user credentials before logging the user in to the service.

This variation on input capture may be conducted post-compromise using legitimate administrative access as a backup measure to maintain network access through External Remote Services and Valid Accounts or as part of the initial compromise by exploitation of the externally facing web service.

## Kill Chain Phase

- Collection (TA0009)
- Credential Access (TA0006)

**Platforms:** Linux, macOS, Windows

## What to Check

- [ ] Identify if Web Portal Capture technique is applicable to target environment
- [ ] Check Linux systems for indicators of Web Portal Capture
- [ ] Check macOS systems for indicators of Web Portal Capture
- [ ] Check Windows systems for indicators of Web Portal Capture
- [ ] Verify mitigations are bypassed or absent (1 known mitigations)
- [ ] Assess detection coverage (1 detection strategies)

## How to Test

### Manual Testing

1. **Identify Attack Surface**: Determine if the target environment is susceptible to Web Portal Capture by examining the target platforms (Linux, macOS, Windows).

2. **Assess Existing Defenses**: Review whether mitigations for T1056.003 are in place. If defenses are absent or misconfigured, this technique may be exploitable.

3. **Execute Test**: Use tools and methods described in the MITRE ATT&CK page and external references below.

> **Note**: No Atomic Red Team tests available for this technique. See [Atomic Red Team GitHub](https://github.com/redcanaryco/atomic-red-team) for updates.

## Remediation Guide

### M1026 Privileged Account Management

Do not allow administrator accounts that have permissions to modify the Web content of organization login portals to be used for day-to-day operations that may expose them to potential adversaries on unprivileged systems.

## Detection

### Detection of Credential Harvesting via Web Portal Modification

## Risk Assessment

| Finding                                 | Severity | Impact     |
| --------------------------------------- | -------- | ---------- |
| Web Portal Capture technique applicable | High     | Collection |

## CWE Categories

| CWE ID  | Title                             |
| ------- | --------------------------------- |
| CWE-200 | Exposure of Sensitive Information |

## References

- [Volexity Virtual Private Keylogging](https://www.volexity.com/blog/2015/10/07/virtual-private-keylogging-cisco-web-vpns-leveraged-for-access-and-persistence/)
- [Atomic Red Team - T1056.003](https://github.com/redcanaryco/atomic-red-team/tree/master/atomics/T1056.003)
- [MITRE ATT&CK - T1056.003](https://attack.mitre.org/techniques/T1056/003)