About Deflect

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Deflect is a DDoS-mitigation service for NGOs, civil society groups, activist bloggers and independent media. Built by digital security non-profit eQualit.ie, the service is a free, open source and effective solution to mitigate DDoS attacks.


Most human rights and independent media groups do not have the financial or technical resources to mitigate DDoS attacks, so Deflect was created to provide this service free of charge. These attacks — undertaken by infected 'bots' — can disable the targeted website and prevent access for legitimate users, intimidating site owners and stifling free speech on the Internet.

Commercial DDoS mitigation services are expensive and may alter their terms of service if they believe a particular website is drawing very heavy traffic. Many of our partners have come to us after a disappointing experience with a well-known commercial service.

Our approach[edit]

We set up distributed reverse proxy caches on a collection of geographically distributed, low-cost hosting providers. Each host is functionally equivalent, though we are learning which are the best quality providers. Using short time-to-live DNS, distributed caching, IP blacklisting and other identified practices, Deflect services multiple clients simultaneously at a low cost for us and zero cost to them.


Deflect is designed as a robust, low cost, non-proprietary and easily reproducible system to provide protection to multiple websites, which we call "Origins".

The system was created to remain neutral to different web servers, with some limitations detailed below. It is built using Debian 6 VPSs, which we call "Edges", and a controlling server we call "Controller". The caching component is handled by Apache Traffic Server.

Protection offered[edit]

  • Absorbing 99%+ of traffic destined to your website. Check out our traffic stats.
  • Hiding your server's location (IP address).
  • Preventing public access to editorial dashboards (e.g. /admin, /login, etc.).
  • Filtering out malicious requests using fail2ban, learn2ban and iptables rulesets.

Deflect in Action[edit]

To access a Deflect-protected website:

  1. Enter the website's address in the browser.
  2. The DNS will retrieve an alias pointing to our pool of edges. One of these edges is then selected using round robin DNS.
  3. If the requested address is permitted and the edge has the content of the page in its cache, it will immediately reply to the browser. If the content is not cached on the edge, it will be requested from the origin and sent to the browser.
  4. If the address is not permitted, a notification page is displayed.

The picture below gives a simple explanation:


Details and limitations[edit]

Cached Components[edit]

Deflect handles web pages composed of many elements, including CSS, Javascript, multimedia and large binary files. Page components that are hosted on different domains ("widgets," traffic trackers, etc) are handled in the regular manner.

Deflect currently caches responses for 10m, which can be tuned for individual locations (longer for infrequently changing binary files, shorter for online forums for example).


While Deflect currently ignores cookies, returning the same object from the cache regardless of any cookies present in the client request, it is configurable on a per-domain and per-path basis. We can enable unique treatment of different cookies for a site or part of a site, however we effectively disable our ability to cache that site or part of site. Nevertheless, the site will still be protected by our firewall analysis. Query strings are treated as part of the URL - different query strings will always be considered unique objects and cached as such. Responses to POST requests are never cached.

Is it working?[edit]

You can tell Deflect is serving a page by looking at the HTTP headers (using 'Inspect Element' on Chrome or Firefox); you'll see a Via: string that returns an individual edge serving the requested webpage. It will look similar to:

Via:http/1.1 prometeus1.deflect.ca (ApacheTrafficServer/3.2.4 [uIcMsSfWpNeN:t cCMi p sS])

The caching response, in the above case [uIcMsSfWpNeN:t cCMi p sS] can be interpreted here.


Deflect also supports SSL. For further information, see this page.


DNS is configured for short TTL ("time to live") to allow rapid addition/removal of nodes to the edge pool.

If you have any more questions, please see our FAQ or drop us an email and we'll do our best to answer it.

Deflect Customizations[edit]

Over time, we're developing profiles for different Web servers. In the meantime, we can provide customization for the following:

  1. Domains and their aliases (www.yoursite.org, yoursite.org)
  2. Cache "time to live"
  3. Protected locations (/admin)