Most crypto security writing focuses on what happens on-chain: malicious approvals, wallet drainers, phishing domains pushing signature scams. But a large and growing share of real losses never touches a blockchain exploit at all. They start when a trader double-clicks a “free trading bot,” a game cheat, or a cracked copy of some software — and a piece of malware called an infostealer spends the next ninety seconds quietly copying everything on the machine that opens doors.

This is currently one of the biggest raw materials industries in cybercrime. Security firm Cloudflare reported an 11-fold increase in traffic from known infostealer command-and-control servers in the first half of 2025 compared to a year earlier. Microsoft and the US Department of Justice have each taken swings at the operators — and the market kept growing anyway.

This article walks the full chain: what these tools actually steal, why stolen cookies beat your 2FA, how the logs become crypto theft, what the 2025 takedowns did and didn’t change, and the short list of defenses that actually break the attack.

BLUF: Infostealers attack the computer, not the chain. Anything that lives on your machine in digital form — browser sessions, saved passwords, wallet extension vaults, Telegram logins, seed-phrase text files — is presumptively sellable. The structural fix is the same as everywhere else in crypto security: keep long-term holdings in self-custody on a hardware wallet with a seed phrase that has never been typed into a file, and treat your everyday desktop as untrusted territory.

What an Infostealer Actually Does

An infostealer is single-purpose malware. It doesn’t encrypt your files for ransom, doesn’t linger, doesn’t spread on its own. It runs once when you execute the payload, does its harvest in 30 to 90 seconds, sends the bundled “log” to the operator’s server, and in many cases deletes itself. From the victim’s point of view, nothing visible happens. That’s the product design.

A typical harvest includes:

  • Browser session cookies — the live login tokens for every site where you clicked “remember me.” This is the crown jewel, and most people underrate it.
  • Saved passwords and autofill — anything your browser memorized: exchanges, webmail, bank portals, CEX accounts.
  • Crypto wallet extension data — the encrypted vault files from browser wallets like MetaMask. Encrypted, yes — but now the attacker owns a copy and can crack it offline at leisure.
  • Desktop wallet files — any wallet.dat-style files found in common locations.
  • Telegram Desktop sessions — Telegram sessions are portable; a stolen session is a live account, including groups and any 2FA codes routed there.
  • Everything that looks like a seed phrase — the malware scans Documents, Desktop, and Downloads for text files whose names or contents match patterns like “seed,” “wallet,” “mnemonic,” “password.” If your recovery phrase lives in a note file, this step finds it.

The log is then compressed and uploaded. Within hours it is for sale.

Why Stolen Cookies Beat Your 2FA

Here is the part that surprises people: the attacker who buys your log does not need your password, and never sees your one-time code. Both protections guard the login screen. A stolen session cookie skips the login screen entirely — it replays the “already logged in” state to the site.

Concretely:

  1. Webmail cookie → everything. A Gmail or Outlook session is a master key. From inside your email, an attacker resets passwords on exchanges, intercepts the reset links, and enrolls their own 2FA. Your email provider never shows a login prompt because the session is already valid.
  2. Exchange cookie → trading float. Direct replay into a logged-in exchange account. Withdrawal confirmations sometimes route through email or SMS — which is why stealer operators also harvest Telegram sessions and why the same personal data in your log feeds SIM swap attempts against your phone number.
  3. No lockout, no alert. Many services show “new login” warnings for fresh logins but stay quiet for sessions that look continuous. Cookie replay looks continuous.

This is why “I have 2FA everywhere” is not the safety net people assume. Two-factor authentication protects authentication; a stolen session is authentication. The defenses that matter are the ones in the stack below — session hygiene, device separation, and withdrawal friction.

The Crypto-Specific Targets

Generic credential theft is old news. Three targets make crypto users a premium market for stealer logs:

Wallet extension vaults. When you set up MetaMask or a similar browser wallet, the extension encrypts your seed phrase with a password you choose. The vault file is small and lives in a predictable folder. Security researchers demonstrated back in 2023 that these vaults can be cracked offline when the extension password is weak — and criminal services now openly advertise vault-cracking alongside log sales. If your browser password is Password123, the encryption is decorative.

Seed-phrase files. The single worst habit in crypto is storing a recovery phrase digitally: a note file, a screenshot, a draft email, a cloud-synced document. Infostealers explicitly search for these by filename and content pattern. A seed phrase in a text file converts a 90-second malware run into total wallet loss — no cracking, no skill required.

Session bundles. A log containing a webmail cookie plus an exchange cookie plus a Telegram session is a complete account-takeover kit. Buyers of these logs specialize in the aftermath: draining exchanges, locking out the owner, and sometimes waiting days or weeks for a deposit to land before emptying the account.

The Economy: Logs for Sale

Infostealers are sold as a service — malware-by-subscription, often a few hundred dollars a month, with customer support, admin panels, and build generators. The operators run the malware; the customers run distribution. A second tier of brokers aggregates stolen logs and sells them in bulk on Telegram channels and dark-web markets, sometimes with “checker” services that pre-validate which logs contain live exchange sessions or crypto wallets.

The 2025 takedowns gave a public look at the scale:

  • Operation Magnus (October 2024). Dutch police, working with the FBI and Europol partners, seized the infrastructure of RedLine and TripleA — at the time among the most-used stealers globally.
  • Lumma takedown, round one (May 2025). Microsoft’s Digital Crimes Unit won a court order and, with international partners, took down roughly 2,000 machines relaying Lumma’s command traffic. In the two months of telemetry around the action, Microsoft observed about 394,000 Windows devices infected with Lumma.
  • Lumma takedown, round two (October 2025). After Lumma partially rebuilt, Dutch police and the US DOJ announced a second seizure of its domains and infrastructure.

Each takedown dented a brand, not the category. New families — StealC, RisePro, and post-Lumma entrants like Meduca — absorbed the demand within weeks. The lesson of 2025 is that stealer infrastructure is replaceable in a way that, say, a bridge exploit is not. Which puts the burden back on the defensive side.

How the Payload Reaches a Crypto User

The malware needs one thing from you: an execution. Distribution is social engineering with a file attached. The crypto-native vectors worth knowing:

  • “Free trading bots” and “airdrop checker” tools — executables or scripts posted on Telegram and Discord that promise automation. The tool never needs to work; the double-click is the product. The developer-side variant of this — poisoned npm packages — is covered in npm supply chain attacks.
  • Fake moderator and job interviews — the classic playbook where a “recruiter” walks you through downloading a “meeting app.” That installer is the entire point of the exercise, as described in the social media scam playbook.
  • Malicious search ads for wallet software — paid results above the real site, serving lookalike downloads. The same vector drives phishing scams and fake wallet apps; with stealers, the fake site hands you malware instead of asking for a seed phrase.
  • Cracked software and game cheats — the commodity channel, huge volume, no crypto targeting needed. If your daily machine runs pirated software, assume logs of it are for sale somewhere.
  • Crypto-branded installers — fake versions of popular desktop wallets or tooling, pushed through typosquatted domains and file-sharing sites.

One machine, one execution, one log. Everything after that is triage by the buyer.

The Kill Chain, End to End

Putting it together from the attacker’s chair:

  1. Distribution. A target downloads the payload from one of the channels above and runs it, often with antivirus quietly bypassed via obfuscation or a “disable your protection” instruction in the install steps.
  2. Harvest. Thirty to ninety seconds: cookies, saved passwords, wallet vaults, Telegram session, candidate seed files.
  3. Sale. The log lands on a market within hours, priced by content. Logs with live exchange sessions or wallet vault files command a premium.
  4. Triage. The buyer tests sessions — email first, then exchanges. Wallet vaults go to cracking if the password looks weak.
  5. Drain. Exchange balances move to fresh addresses; self-custody wallets drain if a seed file or crackable vault was found. Withdrawal allowlists and delay locks are sometimes the only thing standing between a replayed session and your float.
  6. Aftermath. Expect the follow-on wave: “recovery agents” who target victims — read the recovery scam anatomy before answering strangers.

The Defense Stack

Ordered by what actually breaks the chain:

1. No digital seed phrases. Ever. The seed phrase for long-term holdings lives on paper or metal, generated on a hardware wallet, never typed, photographed, screenshotted, or synced. This single rule defeats the highest-value theft paths outright.

2. Separate the machine that touches money. The browser profile (or better, the device) that holds wallet extensions and logs into exchanges runs nothing else — no cracked software, no Telegram-downloaded tools, no random installers. A cheap laptop used only for crypto is cheaper than one drained account. This mirrors the segmentation logic in how to prevent wallet drainers, applied at the OS level.

3. Prefer apps and hardware keys over saved web sessions. Exchange mobile apps don’t share your desktop browser’s cookie jar, and native apps are outside the classic browser-stealer template. For web logins that matter, use a hardware security key — it raises the cost of fresh logins even though it can’t undo an existing stolen session, which is why step 4 exists.

4. Kill sessions and add withdrawal friction. Log out of exchange web sessions instead of staying signed in for weeks. Enable withdrawal address allowlists with a 24-hour delay on changes — a replayed session can request a withdrawal, but a delay lock gives you the window to catch the “new withdrawal address” alert from a device the attacker doesn’t control. On the account side, the same hygiene that blunts SIM swapping helps here, since both attacks converge on the email-plus-phone recovery layer.

5. Treat execution as consent. The moment you run an untrusted executable, assume the log is already uploaded. Don’t rationalize (“it was only a bot, it didn’t ask for admin”). Stealers don’t need admin rights.

6. If it happened, rotate everything from a clean device. Not just passwords — sessions. Change the email password first, revoke all sessions on every exchange and webmail account, then move funds: exchange float to a fresh address, self-custody to a wallet with a brand-new seed. A new address under the old seed is not safe if the vault file or any seed-adjacent file was on that machine. The response playbook is the same first-hours discipline as any account takeover — see what to do in the first 24 hours after a theft.

Limitations

  • Session replay is not fully solvable client-side. Even disciplined users can’t fully prevent cookie theft on a general-purpose OS; the realistic goal is making your log low-value (no wallets, no seed files, no long-lived sessions) rather than making the machine unhackable.
  • Antivirus is a speed bump, not a wall. Stealer builders are tested against mainstream scanners before release. The distribution vectors that matter are decisions, not detection gaps.
  • Mobile is safer, not safe. Infostealers overwhelmingly target Windows, but mobile malware and malicious APKs exist — sideloading a “wallet tool” on Android re-creates the same problem in your pocket.
  • This is general education, not a verdict on any specific product. Wallet, exchange, and OS security features change; verify current options for session management and withdrawal locks on the platforms you use.

Frequently Asked Questions

Can infostealer malware steal crypto from a hardware wallet?

No — the device itself signs offline and never exposes the seed to your computer. What infostealers do steal is anything digital near the wallet: seed phrases saved as text files or screenshots, weakly-encrypted wallet extension vaults on the same machine, and exchange/webmail sessions that control your trading float. A hardware wallet plus a seed phrase that has never existed in digital form is outside the infostealer's reach.

If I use a password manager and 2FA everywhere, am I safe?

Partially. Most infostealers target browsers' built-in password stores and session cookies, which a password manager avoids — but the session cookie bypass means even perfect passwords don't protect a logged-in browser. And 2FA does nothing when the attacker reuses a valid session instead of logging in. Treat 2FA as protection against logins, not against cookie theft, and close sessions on machines that run untrusted software.

I ran a suspicious file that I thought was a trading bot. What now?

Act on the assumption that everything on that machine is already in someone's log. From a different, clean device: change your email password first, revoke all active sessions on email and exchanges, sweep exchange balances to a fresh address, and move self-custody funds to a wallet with a brand-new seed phrase (a new address under the old seed is not enough if the vault file was stolen). Only then disinfect or wipe the machine.