Is curl pipe bash safe? How to check before you run it

Q: Is curl | sudo bash worse?

Yes. `sudo` gives the script every permission on the computer, not just your own files, so a bad script can install itself system-wide and change anything. Run an installer as your normal user first. If it says it needs administrator rights, read the script to see what it does with them before you agree.

Q: How do I read an install script before running it?

Download it without running it (`curl -fsSL -o install.sh ` on macOS and Linux, `Invoke-WebRequest -Uri -OutFile install.ps1` on Windows), open it in a text editor or with `less install.sh`, and check where it downloads from, what it changes and whether anything is scrambled. If you cannot read a part of it, do not run it.

Q: Is irm | iex on Windows the same thing?

Yes. `irm | iex` downloads text and runs it at once, exactly like `curl | bash`. It also skips PowerShell's execution policy, because no script file is involved, and Microsoft says that policy is a safety feature, not a security boundary. The same advice applies: download to a file, read it, run the file.

Is curl pipe bash safe? It is the line that ends curl -fsSL <address> | bash: it downloads a script and hands it straight to your shell, which runs it with every permission you have. Homebrew, Rust and Claude Code all tell you to install that way, so the habit is everywhere. That is exactly why attackers copy it.

In 2026, researchers found fake install pages for Homebrew and Claude Code, bought as search ads, that showed the same kind of one-line command with a different address in it. Pasting it ran a stealer that took browser logins, wallets and, in one case, SSH and cloud keys. This guide shows how to tell the difference, how to read a script before it runs, and which installs do not need a script at all.

What does curl | bash actually do?

curl | bash downloads a text file from a web address and runs it as a program, in one step, without ever saving it where you can look at it. The four letters you type trust four things you cannot see:

The flags in curl -fsSL are ordinary: -f fails on an HTTP error instead of saving an error page, -s hides the progress bar, -S still shows errors, and -L follows redirects. Nothing in them checks the content.

Two details make the pipe worse than a plain download. First, bash does not wait for the whole script: it runs each line as it arrives, so a download that breaks halfway leaves a half-run installer.

Second, a server can tell the difference between you looking at a script and you piping it. A 2026 write-up by Thomas Ferdinand shows how: when bash pauses to run a slow command, curl's buffer fills and the server sees the delay, so it can send a different continuation. Looking at the address in your browser first proves nothing about what the pipe receives. HTTPS does not change that: it secures the connection to the server, not the server's choices.

When is a curl | bash install fine?

A curl | bash command is fine when it comes from the vendor's own documentation, you reached that page yourself, and the domain in the command is the vendor's. That describes Homebrew, rustup and Claude Code: each publishes the command on its own site, and it is the way many people install them every day.

Fine is not the same as risk-free. The risk you accept is that the vendor's server, and everything between its maintainers and your computer, is intact today. It has gone wrong before. Codecov's Bash Uploader, a script that thousands of build systems ran, was quietly modified between January and April 2021 to send out the environment variables of the machines that ran it. It was found when a customer compared the checksum Codecov published on GitHub with the one of the file they downloaded. That one comparison, which a pipe makes impossible, is the whole case for the steps below.

Many vendors now offer a better path next to the one-liner. Claude Code's own setup page lists the script, a Homebrew cask, WinGet, and signed apt, dnf and apk repositories, and publishes a signed manifest of checksums with the key's fingerprint. Homebrew offers a .pkg installer for interactive or managed installs. When a vendor gives you a choice, the one your package manager verifies is the safer one.

How attackers use curl | bash against you

Attackers do not need to break a vendor. They only need you to paste the wrong line, and the one-line habit makes the wrong line look right. Security researchers named this InstallFix: a cloned install page, reached through a search ad, with a command that is close to the real one.

Push Security described it in March 2026 with fake pages for Claude Code, Homebrew and other developer tools, shown above the real documentation as sponsored Google results. Hunt.io found fake Homebrew pages where only the domain in the command had changed, and 49 similar pages built the same way. In May, Trend Micro reported ads bought for the search "Claude Code install". In August, Huntress traced a Mac intrusion to a sponsored result that led to a page under the real claude.ai address: a shared conversation, dressed up as an Apple Support install guide. A correct-looking address bar is not proof.

Here is how it looks from your side, with a made-up tool:

How a fake install page runs a stealerBuilt on the InstallFix reports from Push Security, Hunt.io, Trend Micro and Huntress. The tool, the domains and the program are made up and the commands are defanged

With antitheft

With antitheft, the stealer is stopped at your passwords

Caught the moment it reaches for your passwords or wallets
On Linux refused before the file opens, on Windows and macOS stopped right after
Even the most advanced malware, the kind no antivirus has seen yet

antitheftCRITICALjust now

zbxhelper.exe tried to read Google Chrome's saved passwords - stopped

zbxhelper.exe

C:\Users\you\AppData\Roaming\zbx\zbxhelper.exe

Touched: Google Chrome - Saved passwords
Type: Storage access

KILLNOT A THREATVIEW DETAILS

antitheftCRITICALjust now

zbxhelper tried to read Google Chrome's saved passwords - stopped

zbxhelper

/Users/you/Library/Application Support/zbx/zbxhelper

Touched: Google Chrome - Saved passwords
Type: Storage access

KILLNOT A THREATVIEW DETAILS

antitheftCRITICALjust now

zbxhelper tried to read Google Chrome's saved passwords - blocked

zbxhelper

/home/you/.local/share/zbx/zbxhelper

Touched: Google Chrome - Saved passwords
Type: Storage access

KILLNOT A THREATVIEW DETAILS

Keep stealers out of your passwords and wallets

Guards passwords, browser logins and wallets
Stops malware your antivirus misses
On Windows, macOS and Linux

See what antitheft protects

Here is exactly what that alert covers. On Linux, the antitheft app refuses any program that is not the owner when it reaches for browser passwords, logins, session cookies and wallets, and that includes a program a script started. On Windows and macOS it stops that program the moment it touches them. The script itself still runs, because from the system's view you started it yourself, as you.

The habits below come first: they keep the script from running at all.

For power usersWhy the paste warning is not a defense

Microsoft notes that scripts launched through Terminal do not get the Gatekeeper checks (signing, notarization) that apps opened through Finder can. macOS Tahoe 26.4 added a warning that can block a paste into Terminal ("Possible malware, paste blocked"), but Apple has not documented which commands trigger it, and Malwarebytes reported the same unknown. Treat it as a second chance, not a check you can rely on.

How to check a script before you run it

To check an install script, download it to a file instead of piping it, read it, compare its checksum with the vendor's published one, and only then run that exact file. Running the file you read closes the two gaps the pipe leaves open: the server cannot change its answer between your look and your run, and a broken download cannot half-run.

This takes about two minutes. None of the commands below run the script.

Downloading, reading and running an install scriptzorbex and get.zorbex.example are made up (.example addresses do not exist). The commands are curl, less, shasum and sha256sum, and PowerShell's own cmdlets

The hash step is only as good as where the expected value comes from. If the vendor publishes it, take it from the vendor's own site or release page, not from the same place you got the script. If it publishes nothing, skip the step and rely on reading. A mismatch means do not run it: that is the Codecov check, and it is what caught that incident.

On Windows, a downloaded .ps1 may refuse to run. PowerShell's execution policy is the reason: with no policy set, Windows clients default to Restricted, which blocks all script files. Microsoft calls the policy a safety feature and not a security boundary, since typing the script's contents at a prompt gets around it, which is also why irm | iex ignores it. Do not loosen your whole machine for one script. Use the vendor's winget package or signed installer instead.

For power usersWhat the checks do and do not prove

curl -fsSL -o install.sh <address>: -o writes to a file instead of the screen, so nothing is executed. Add --proto '=https' --tlsv1.2 (as the Rust installer's command does) to refuse a downgrade to plain HTTP.
bash -c "$(curl -fsSL <address>)", the form Homebrew uses, waits for the whole download before running, so a cut connection cannot half-run it. It is still unreviewed code, so the same inspection applies.
sha256sum -c: put the vendor's value and name in a file as <hash> install.sh, run sha256sum -c thatfile (or shasum -a 256 -c on macOS) and read install.sh: OK.
A matching checksum proves the file is the one the vendor published. It does not prove the vendor's published value was not changed together with the file, which is why a signature (the signed manifest Claude Code publishes, checked with gpg --verify) is stronger.
Reading proves what this script does, not what the programs it downloads next do. A script that fetches a second program from a domain that is not the vendor's is the line to stop on.
Never sudo bash first. Run as your user, and read what the script says it needs administrator rights for.

curl | bash or a package manager: which is safer?

A package manager install is safer than an install script when the vendor offers it, because the package manager checks a signature on what it installs and keeps a record you can undo. A script checks nothing and leaves nothing to undo. Roughly, from most to least checked:

A signed repository (apt, dnf, apk) with the vendor's key fingerprint: the package manager verifies every package. Claude Code publishes these and tells you to check its key against the fingerprint on its page.
A package manager or store such as Homebrew casks or WinGet: someone else's review and your tool's integrity checks, and a clean uninstall.
A vendor installer (.pkg, .msi, a signed .exe): your system can check its signature, and macOS and Windows show you the publisher before it runs.
Download, read, verify, run the script: the steps above.
curl | bash straight from a page: the one-liner, with nothing between you and a bad day.

Trend Micro's advice after the Claude Code ads is the same: prefer official package managers over scripts from third-party sites, and do not copy commands from pages reached through sponsored results. Installing with a package manager is also a case where antitheft does more: on Linux, what a package's install script runs is refused your browser passwords, logins and wallets, and cannot add itself to the places that start with your computer. That covers package-manager installs and not a script piped into bash.

For a worked example of checking a package before installing it, see how to check if an npm package is safe.

What to do if you already ran a script you did not trust

If you ran a script from an ad, a chat answer or a page you cannot vouch for, treat the computer as if a stealer ran. A script from a vendor's own page that matches its published checksum needs no action.

Disconnect the computer from the internet.
From a different, clean device, move your crypto first. Create a new wallet with a new seed phrase and send your funds there. A transfer cannot be reversed.
Change your email password first, then your banking, exchanges, password manager and social accounts, and sign out of every session so stolen logins stop working.
Rotate developer secrets: SSH keys, cloud keys, GitHub and package registry tokens, and the values in .env files. antitheft shows you which apps read them; until you have rotated them, treat them as exposed.
Look for what it left behind: new startup items, scheduled tasks, launch agents or cron jobs you did not create.
Reinstall the system before you trust the computer again. What to do if your passwords were stolen covers the accounts.

How to protect yourself from malicious install scripts

Protection here is mostly a habit: the command has to come from the vendor's own site, and you should not run it as one unread line. These six habits cover almost every case:

Never use a command from an ad, a chat answer or a message. Go to the vendor's site by its own address or a bookmark.
Compare the domain in the command with the vendor's, letter by letter. Hunt.io's fake Homebrew pages changed one domain and nothing else.
Prefer a package manager or a signed installer when the vendor offers one.
Download, read and verify a script before you run it.
Do not use sudo for the first run.
Stop at anything scrambled, at a second download from another domain, or at anything you do not understand.

On top of the habits, antitheft is the safety net for the moment one of them fails. On Linux, only the app that owns your browser passwords, logins, session cookies and wallets can open them, so a program an unread script started is refused; on Windows and macOS antitheft stops it the moment it touches them. Its Activity view shows you which programs opened your SSH keys, .env files and developer tokens. It does not replace your antivirus or the habits above.

If the fake page reached you through a search ad, fake ads for real apps explains how to spot a poisoned result, and the fake CAPTCHA scam is the same paste-and-run trick with a different costume.

Questions people ask

Is curl | bash safe?

It is as safe as the page you copied the command from, the server it names and the connection in between, and you cannot check any of them once it runs. With a vendor's own documentation, typed or bookmarked by you, the risk is the vendor's own security. With a command from an ad, a chat answer or a page you reached through search, it can be an attack. Download the script to a file, read it, then run the file.

Is curl | sudo bash worse?

Yes. sudo gives the script every permission on the computer, not just your own files, so a bad script can install itself system-wide and change anything. Run an installer as your normal user first. If it says it needs administrator rights, read the script to see what it does with them before you agree.

Does HTTPS make curl | bash safe?

HTTPS proves you reached the server the address names and that nobody changed the data on the way. It says nothing about what that server chooses to send, or whether the address is the one you meant. A look-alike domain has a perfectly valid HTTPS lock, and a server can send one script to a browser and another to curl | bash.

Why do Homebrew, Rust and others tell you to use curl | bash?

Because it works on every system with one line and no account, and because the vendor controls the server. Homebrew, rustup and Claude Code all publish such a command on their own sites. The pattern is not the problem. The problem is that attackers copy the same one-line look, and the one-line habit gives you no way to tell the real command from the fake.

How do I read an install script before running it?

Download it without running it (curl -fsSL -o install.sh <address> on macOS and Linux, Invoke-WebRequest -Uri <address> -OutFile install.ps1 on Windows), open it in a text editor or with less install.sh, and check where it downloads from, what it changes and whether anything is scrambled. If you cannot read a part of it, do not run it.

Is irm | iex on Windows the same thing?

Yes. irm <address> | iex downloads text and runs it at once, exactly like curl | bash. It also skips PowerShell's execution policy, because no script file is involved, and Microsoft says that policy is a safety feature, not a security boundary. The same advice applies: download to a file, read it, run the file.

Can antitheft stop a malicious curl | bash script?

It does not block the script and it does not read it. It protects what a stealer the script starts goes for: on Linux, only the app that owns your browser passwords, logins, session cookies and wallets may open them, so the stealer is refused even if nobody has seen it before; on Windows and macOS antitheft stops it the moment it touches them. Its Activity view also shows you which programs read your SSH keys, cloud keys, tokens and .env files, so you know what to rotate. Blocking of start-up entries covers package-manager installs on Linux only.

the short version

Is curl pipe bash safe? Only as safe as the page you copied the command from and the server it names, and the one-line form hides both. A vendor's own command from its own site is a normal risk. The same line from an ad, a chat answer or a search result can be an attack. Download the script to a file, read it, check its checksum if one is published, then run the file.

sources

What does curl | bash actually do?

When is a curl | bash install fine?

How attackers use curl | bash against you

How to check a script before you run it

curl | bash or a package manager: which is safer?

What to do if you already ran a script you did not trust

How to protect yourself from malicious install scripts

Questions people ask

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