Cloudflare Improves DDoS Mitigation Tool
23.5.18 securityweek Safety

Cloudflare announced a series of improvements to its Rate Limiting distributed denial of service (DDoS) protection tool this week.

Over the past six months, the company has observed an uptick in application (Layer 7) based DDoS attacks and also noticed that the assaults aren’t using huge payloads (volumetric attacks), but rely on a high number of requests per second to exhaust server resources (CPU, Disk and Memory). Attacks with over 1 million requests per second are a common thing, Cloudflare says.

Launched by the web infrastructure company a year ago, the Rate Limiting feature helps customers protect their web applications and APIs from various attacks, including DDoS, credential stuffing and content scraping.

In addition to the previously available Block and Simulate options, the tool now provides customers with Cloudflare JavaScript Challenge and Google reCaptcha (Challenge) mitigation actions available in the UI and API. Additionally, the company claims to have made Rate Limiting more dynamically scalable.

“A new feature has been added which allows Rate Limiting to count on Origin Response Headers for Business and Enterprise customers. The way this feature works is by matching attributes which are returned by the Origin to Cloudflare,” the web protection company notes.

For the credential stuffing protection, for example, Cloudflare customers can set a single rule (a Basic rate limit) or multiple rules (Advanced limits) to prevent abuse, depending on their needs. This ensures that only users (which typically enter a wrong password three times before hitting the recovery option) log in, and not bots (which go through thousands of credential combinations to see what works).

“With this type of tiering, any genuine users that are just having a hard time remembering their login details whilst also being extremely fast typers will not be fully blocked. Instead, they will first be given out automated JavaScript challenge followed by a traditional CAPTCHA if they hit the next limit. This is a much more user-friendly approach while still securing your login endpoints,” Cloudflare points out.

Cloudflare’s tool also includes a new origin headers feature that allows customers to configure their origin to respond with a header to trigger a rate-limit. A header is generated at the origin, and added to the response to Cloudflare.

“As we are matching on a static header, we can set a severity level based on the content of the Header. For example, if it was a repeat offender, you could respond with High as the Header value, which could Block for a longer period,” Cloudflare explains.

Rate Limiting can also protect from the increasingly popular enumeration attacks, the company says. Such assaults rely in identifying an expensive operation in an app and then overload it to exhaust resources and slow or crash the app.

To fend off such attacks, one can set a rate limit for the 404 (page not found) response a query sent to the app receives when the user is not found. Thus, if the threshold of 404’s is crossed in a given period of time, the app can be set to challenge the user to prove they are a real person.

To mitigate content scrapping, Rate Limiting includes support for rules to distinguish between users who browse heavily and bot attempts to copy content for redistribution or reuse. The tool counts the number of requests to each endpoint and the number of hits to the image store, as well as the number of served 404 and 403 pages.

Cloudflare also decided to increase the number of available rules for Pro and Business customers, for no additional charge. Thus, Pro plans now include 10 rules, while Business plans include 15 rules.