Subtlety is out when it comes to compromising user credentials. Instead, cybercriminals are looking to brute-force their way in, take what they can and get out. Consider the case of GitHub: As noted by TechCrunch, the online code repository recently announced that there have been “unauthorized attempts to access a large number of GitHub.com accounts” using credentials stolen from other hacked sites.

According to technology firm Akamai, these account takeover (ATO) tactics are becoming popular attack vectors: In one week — Feb. 10–17, 2016 — the company analyzed a financial services attack using more than 990,000 distinct IPs that checked over 427 million accounts. Put simply? Brute force is back.

Risky Recycling?

It’s no surprise that users recycle passwords and login credentials. Between workplace authentication, social accounts and e-commerce details, it’s hard to keep track of multiple access pairs. Attackers are aware of this tendency and use it to full effect by striking out with ATO or credential stuffing attacks.

It works like this: Using multiple IP and email addresses, cybercrooks leverage stolen password and login data to attempt brute-force logins to financial, e-commerce or other high-value sites. While some users heed the advice of IT professionals and either don’t use or regularly change their access details, others haven’t been so diligent.

The result? Cybercriminals gain access and may be able to log into other services using the same credentials again and again. While recycling makes sense for paper and plastic, passwords are off the table.

Akamai Finds Rapid Reuse

As noted by Softpedia, the attacks uncovered by Akamai targeted both a financial services and entertainment company during the ATO blitz in February. This wasn’t just dipping a toe in the water; both attacks finished stronger than they started, using 993,547 and 817,390 IP addresses on day seven compared to 248,387 and 163,478 on day one.

Akamai became aware of the credential-stuffing crush after 22,555 WAF-blacklisted IPs were used. The crooks leveraged a combination of proxy servers, compromised home routers and modem-based botnets to achieve massive throughput.

Here, speed trumps success: With credentials now widely available on both public sites and deeper into the Dark Web, there’s virtually no risk for attackers if they’re refused entry — users will get a password change notification, but cybercrooks are essentially in the clear.

The moral of the story? Credential stuffing works because accessing password/login combinations isn’t hard for motivated cybercriminals, especially if sites don’t properly hash or otherwise encrypt this data. Users make it easier by reusing passwords, giving actors everything they need to carry out high-value, low-risk attacks. While sites can do their part by limiting login attempts and looking for rapid-fire IP connections, the ultimate pushback to brute force rests with users: Too much recycling puts identity at risk.