Can Bitcoin be hacked?

Bitcoin is new and fully digital. There’s no bank holding it on your behalf, so it’s natural that many people first think about risks. As a system, Bitcoin has shown for well over a decade how resilient it is to attacks. The blockchain, the shared ledger, is considered extraordinarily hard to manipulate, both technically and economically.

It’s important to separate two things: the security of individual users or platforms, and the security of the Bitcoin network itself. People can lose passwords or fall for phishing. Exchanges can be hacked. That’s different from an attack on Bitcoin’s core infrastructure.

User level vs. network level

• User level: private keys, seed phrase, and passwords. If you’re careless here, you can lose coins without any “hack” of the blockchain.
• Network level: cryptography, the peer-to-peer network, and mining compute power (hash rate). This is where it’s decided whether the system as a whole is vulnerable. Below we focus on the second level: how technically robust is Bitcoin?

The blockchain’s security

Bitcoin is a database maintained by thousands of independent nodes around the world. Anyone can participate. To “hack” this database, compromising a single computer isn’t enough—every other node constantly cross-checks and rejects invalid blocks. The network follows objective rules to determine the valid chain, not majority opinions.

Double-spends

A core promise of Bitcoin: the same unit cannot be spent twice, and no “fake/duplicate” coins can be created. This is enforced by rules that every full node checks independently. A transaction that contains a double-spend won’t be included in a block by miners in the first place, because it would invalidate the entire block. And even if a block were mined that violates the rules, other participants would simply reject and discard it.

51% attack

Often mentioned: the “51 percent attack.” This means trying to build an alternative chain, using more than half of the total compute power, to reverse payments (double-spend), for example. Theoretically possible—practically extremely expensive:

• Cost: You need a majority of global mining power—meaning billions in specialized hardware (ASICs) and electricity.
• Incentives: Even a “successful” attacker would damage market confidence, devaluing their own coin holdings and their expensive hardware.
• Rising hurdle: As Bitcoin usage and price rise, the hash rate rises and so does the cost of any such attack. A 51% attack isn’t “just more computers,” it’s an industrial project: you’d need more compute than all honest miners combined - millions of specialized ASICs worth billions, months-long supply chains, warehouses, cooling, gigawatt-scale power contracts, and a globally distributed operations setup. You also have to sustain that capacity, or honest miners will counter by increasing their own hash rate. Meanwhile, market participants would notice the attack and the BTC price would fall, destroying the attacker’s ability to refinance. In the end, the attacker risks economically wrecking their extremely expensive, Bitcoin-only hardware.

In short: the bigger Bitcoin gets, the less attractive the attempt becomes.

The peer-to-peer network’s robustness

The Bitcoin network consists of tens of thousands of nodes that relay transactions and blocks. An attacker’s goal would be to take nodes offline or disrupt data flow. That’s why developers pay close attention to DoS resilience (protection against denial-of-service) when introducing new features.

One example: Bitcoin Script is intentionally not Turing-complete. If loops were possible, malicious transactions could exhaust node resources and knock them out. That is ruled out by design. Improvements like Erlay (more efficient transaction relay) or Dandelion-style concepts (better source privacy) further target robustness and privacy. In addition, today practically anyone can run their own full node at home for a few hundred euros. The low cost lowers participation barriers and makes the network extremely decentralized in practice.

What if the internet goes down?

Bitcoin primarily uses the internet (like almost all modern services). If the network goes down on a large scale (or is censored), traditional payment systems also start to wobble. For Bitcoin:

• Data stays intact: Every node keeps the blocks it has validated so far locally.
• Finding each other again: As soon as connections return, nodes agree again on the objectively valid (longest) chain.
• Alternative paths: Blocks and transactions can also be distributed via satellite, radio, or mesh networks. These paths are constantly improving and reduce reliance on the traditional internet.

Cryptography: signatures and hashes

Bitcoin’s “trust minimization” stands and falls with proven cryptography:

ECDSA signatures: They let a sender prove they’re authorized to pay—without revealing private keys. This approach has been used for many years, far beyond Bitcoin.

SHA-256 hash function: The core of Proof-of-Work and many other mechanisms. Hashes are one-way and unpredictable.

If either of these were broken, the consequences would be severe not just for Bitcoin, but for large parts of the digital world (banking, TLS/HTTPS, software updates, etc.). In such a case, Bitcoin could migrate to new schemes: painful and not without friction, but fundamentally possible.

The quantum computer threat?

Often cited but rarely concrete: quantum computers. Practical machines that can break today’s cryptography don’t exist. If they did one day—exclusively in an attacker’s hands—the entire digital economy would be at risk, not just Bitcoin.

Two points of orientation:

• Attack surface everywhere: Bank cards, passwords, VPNs, e-commerce—everything would come under pressure.
• Entropy advantage: A credit-card setup is on the order of ~10¹⁹ possibilities; with Bitcoin we’re talking about a keyspace of ≈ 2²⁵⁶ (~10⁷⁷). Even the effective security level against ECDSA attacks is still ~2¹²⁸ (~10³⁸)—both orders of magnitude larger. Here too: if the community identifies concrete weaknesses early enough, the protocol can switch to quantum-resistant schemes.

What’s often confused: “Bitcoin hacked” vs. “user hacked”

When headlines report “Bitcoin theft,” it’s almost always phishing, malware, exchange hacks, or poorly secured private keys—i.e., user or platform failures, not a break of blockchain security.

Final Thoughts

• The Bitcoin blockchain and the network of nodes and miners have proven extremely resilient.
• Theoretical risks exist, but they would hit almost all digital systems equally—not just Bitcoin.
• The biggest everyday risk is human: if you protect keys, devices, and access properly, you massively reduce your exposure.