Over the past few weeks, our Security Operation Center (SOC) has been seeing some different, and very suspicious requests to some of our servers. At first we thought it was a Distributed Denial of Service (DDoS) attack, mainly due to the high concentration of requests (thousands per second). Looking further however, it actually seemed like some DNS resolver was broken and redirecting all their users traffic to us.

Here are some example requests, see for yourself:

GET /100004020560199/picture HTTP/1.1
Host: graph.facebook.com

or

GET /extstyle.css HTTP/1.1
Host: static.ak.facebook.com
User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36

or

GET /wp-content/themes/vip/nesn/images/nesn_favicon_128.png
Host: s0.wp.com

If you do not understand why these requests are interesting, look at the Host: header. It means someone tried to visit static.ak.facebook.com or s0.wp.com and somehow reached our servers. Since we do not host Facebook or WordPress.com, it generates an error on our end.

These were not the only domains that were trying to reach us. Just in the last day, we received requests for: farm4.static.flickr.com, 24.media.tumblr.com, cdn11.optimecdn.com, l.longtailvideo.com, platform.twitter.com, media-cdn.tripadvisor.com, analytics.twitter.com, m.facebook.com, graph.facebook.com, assets.zendesk.com and many other domains.

Why is Facebook, Twitter, WordPress and Zendesk pointing to Sucuri’s Website Firewall (CloudProxy)?

That was a little mystery that took us a bit of time to understand. At first, we thought it was just a new form of DDoS trying to use random domains names to evade our detection.

However, the request headers looked very legitimate. Even via passive fingerprinting, we were able to properly tie the operating system, to the browser and the user agent. It also didn’t look like a DDoS botnet that we could identify. To our surprise, it seemed like real browser requests from valid users.

There was just one catch: all requests were coming from China.

We shared our logs and finding with multiple peers in the security community and the consensus was that these requests were not malicious per se. It seemed as if the Great Chinese Firewall was mis-configured, instead of blocking the requests to certain sites, it was redirecting, to us at that.

So if a specific site was blocked, the requests to graph.facebook.com also got blocked and redirected to us. Same for Twitter, Zendesk or media.tumblr.com.

This explains why most of the requests were actually for CDN, images or API files.

Why is the Chinese Firewall doing that?

That’s a good question and one we do not know the answer to. We can speculate that it is a bug on their end, but can’t be sure. It actually seems similar to the issue that TorrentFreak reported with Pirate bay requests being redirected to random IP addresses.

However, instead of Pirate Bay, it is happening with the most popular platforms and CDNs out there to some of our IP addresses. These “fake” attempts generate thousands of requests per second from thousands of different Chinese IP addresses. It would certainly be enough to DDoS most servers.

Is anyone else seeing something similar?

Full list of domains

If anyone is curious, these are all the domains that reached us just today:

host: “10.media.tumblr.com”,
host: “11.media.tumblr.com”,
host: “12.media.tumblr.com”,
host: “13c3a.http.cdn.softlayer.net”,
host: “15.media.tumblr.com”,
host: “16.media.tumblr.com”,
host: “17.media.tumblr.com”,
host: “18.media.tumblr.com”,
host: “1.media.tumblr.com”,
host: “20.media.tumblr.com”,
host: “22.media.tumblr.com”,
host: “23.media.tumblr.com”,
host: “24.media.tumblr.com”,
host: “26.media.tumblr.com”,
host: “28.media.tumblr.com”,
host: “29.media.tumblr.com”,
host: “2.bp.blogspot.com”,
host: “2-edge-chat.facebook.com”,
host: “2.media.tumblr.com”,
host: “30.media.tumblr.com”,
host: “3-edge-chat.facebook.com”,
host: “3.media.tumblr.com”,
host: “4.media.tumblr.com”,
host: “5.media.tumblr.com”,
host: “6.media.tumblr.com”,
host: “7.media.tumblr.com”,
host: “8.media.tumblr.com”,
host: “987hh.com-www.45878.com”,
host: “9.media.tumblr.com”,
host: “a1.dspnimg.com”,
host: “a248.e.akamai.net”,
host: “a4.ec-images.myspacecdn.com”,
host: “abs.twimg.com”,
host: “accounts.youtube.com”,
host: “ad-audit.tubemogul.com”,
host: “a.deviantart.net”,
host: “adn.6638.edgecastcdn.net”,
host: “ads.exoclick.com”,
host: “ads.gayfriendfinder.com”,
host: “ads.w55c.net”,
host: “am.6park.com”,
host: “analytics.twitter.com”,
host: “api.facebook.com”,
host: “apis.google.com”,
host: “api.twitter.com”,
host: “apps.facebook.com”,
host: “assets1.whicdn.com”,
host: “assets2.whicdn.com”,
host: “assets3.whicdn.com”,
host: “assets.crucial.com”,
host: “assets.mltd.com”,
host: “assets.modelmayhem.com”,
host: “assets.zendesk.com”,
host: “badge.facebook.com”,
host: “banners.videosecrets.com”,
host: “bbc6.global.ssl.fastly.net”,
host: “blogs.ocweekly.com”,
host: “bp0.blogger.com”,
host: “b.s-static.ak.facebook.com”,
host: “cache.armorgames.com”,
host: “cache.blogads.com”,
host: “cdn03.cdn.justjaredjr.com”,
host: “cdn11.optimecdn.com”,
host: “cdn1.barong.inxy-host.com”,
host: “cdn1.editmysite.com”,
host: “cdn1.nudevector.com”,
host: “cdn1.sidhe.co.nz”,
host: “cdn2.editmysite.com”,
host: “cdn2.search.xxx”,
host: “cdn3.aptoide.com”,
host: “cdn3.everyjoe.com”,
host: “cdn3.howtogeek.com”,
host: “cdn5.howtogeek.com”,
host: “cdn.adgear.com”,
host: “cdn.androidcommunity.com”,
host: “cdn.api.twitter.com”,
host: “cdn.collider.com”,
host: “cdn.c.photoshelter.com”,
host: “cdn.easyhotpics.com”,
host: “cdnedge.vinsolutions.com”,
host: “cdn.epom.com”,
host: “cdn.everyjoe.com”,
host: “cdn-frm-sg.wargaming.net”,
host: “cdn.gayboysbox.com”,
host: “cdn.gaycnn.com”,
host: “cdn.gaydudestube.net”,
host: “cdn.gq.com.tw.s3-ap-northeast-1.amazonaws.com”,
host: “cdng.vpnpie.biz”,
host: “cdnimages.gayhits.com”,
host: “cdn-images.mailchimp.com”,
host: “cdn.lfstmedia.com”,
host: “cdn-marketools.plus500.com”,
host: “cdn-mkt.wooga.com”,
host: “cdn.nitrome.com”,
host: “cdn.nudevector.com”,
host: “cdn.porn-lab.com”,
host: “cdn.pornvideospider.com”,
host: “cdn.ps.teenmodels.com”,
host: “cdn.recruitnet.co”,
host: “cdn.sidhe.co.nz”,
host: “cdn.slashgear.com”,
host: “cdn.soundstagedirect.com”,
host: “cdn.tubeporndiet.com”,
host: “cdn.usablenet.com”,
host: “cdn.xgaybox.com”,
host: “cms.myspacecdn.com”,
host: “cn.epochtimes.com”,
host: “cn.wsj.com”,
host: “comps.fotosearch.com”,
host: “content.onhotels.com”,
host: “css.c.photoshelter.com”,
host: “csync.flickr.com”,
host: “cti.w55c.net”,
host: “dc108.4shared.com”,
host: “dc200.4shared.com”,
host: “dc204.4shared.com”,
host: “dc205.4shared.com”,
host: “dc219.4shared.com”,
host: “dc265.4shared.com”,
host: “dc317.4shared.com”,
host: “dc327.4shared.com”,
host: “dc335.4shared.com”,
host: “dc644.4shared.com”,
host: “dc672.4shared.com”,
host: “dc733.4shared.com”,
host: “dingo.care2.com”,
host: “dl6.offercdn.com”,
host: “dl-web.dropbox.com”,
host: “docs.google.com”,
host: “drive.google.com”,
host: “e1.static.hoptopboy.com”,
host: “ecdn.liveclicker.net”,
host: “eg-img.agoda.net”,
host: “eg.img.agoda.net”,
host: “emoneycreater.appspot.com”,
host: “farm1.static.flickr.com”,
host: “farm2.static.flickr.com”,
host: “farm3.static.flickr.com”,
host: “farm4.static.flickr.com”,
host: “farm5.static.flickr.com”,
host: “farm6.static.flickr.com”,
host: “farm7.static.flickr.com”,
host: “farm8.static.flickr.com”,
host: “farm9.static.flickr.com”,
host: “fbstatic-a.akamaihd.net”,
host: “galleries.payserve.com”,
host: “gamemedia.armorgames.com”,
host: “gamerch-static-contents-gz.s3-ap-northeast-1.amazonaws.com”,
host: “graph.facebook.com”,
host: “graphics2.asiafind.com”,
host: “graphics2.asiafriendfinder.com”,
host: “graphics.alt.com”,
host: “graphics.cams.com”,
host: “graphics.outpersonals.com”,
host: “graphics.pop6.com”,
host: “graphics.streamray.com”,
host: “gs1.wpc.edgecastcdn.net”,
host: “i0.wp.com”,
host: “i1.sndcdn.com”,
host: “ia902706.us.archive.org”,
host: “icdn2.digitaltrends.com”,
host: “icdn5.digitaltrends.com”,
host: “icdn6.digitaltrends.com”,
host: “imagena1.lacoste.com”,
host: “imagena2.lacoste.com”,
host: “images.contactmusic.com”,
host: “images.goodsmile.info”,
host: “images.mrskincash.com”,
host: “images.neopets.com”,
host: “images.popin.cc”,
host: “img1.zergnet.com”,
host: “img2.zergnet.com”,
host: “img3.zergnet.com”,
host: “img4.zergnet.com”,
host: “img.docstoccdn.com”,
host: “img.elle.co.jp”,
host: “img.epochtimes.com”,
host: “img.fatxxxtube.com”,
host: “img.kanzhongguo.com”,
host: “img.muji.net”,
host: “img.qz.com”,
host: “img.secretchina.com”,
host: “imgs.ntdtv.com”,
host: “imgx3.dditscdn.com”,
host: “img.youtube.com”,
host: “i.utdstc.com”,
host: “livepassdl.conviva.com”,
host: “l.longtailvideo.com”,
host: “m1.aboluowang.com”,
host: “massmedia-cdn.wistia.com”,
host: “media1.break.com”,
host: “media.247sports.com”,
host: “media-cache-ec0.pinimg.com”,
host: “media-cache-ec2.pinimg.com”,
host: “media-cache-ec4.pinimg.com”,
host: “media.cathkidston.com”,
host: “media-cdn.tripadvisor.com”,
host: “media.dermstore.com”,
host: “media.livepromotools.com”,
host: “media.mademan.com”,
host: “media.sfweekly.com”,
host: “media.skincarerx.com”,
host: “m.facebook.com”,
host: “mobapi.bloomberg.com”,
host: “mobile.twitter.com”,
host: “mzstatic.playhaven.com”,
host: “p1.zdassets.com”,
host: “passets-cdn.pinterest.com”,
host: “pbs.twimg.com”,
host: “photos-a.pe.facebook.com”,
host: “photos.modelmayhem.com”,
host: “photos.pop6.com”,
host: “piclist.pop6.com”,
host: “pic.pimg.tw”,
host: “p.jwpcdn.com”,
host: “platform.twitter.com”,
host: “playstationna.i.lithium.com”,
host: “plus.google.com”,
host: “pmcdn.staticpmrk.com”,
host: “public.oneallcdn.com”,
host: “p.vitalmx.com”,
host: “q-ec.bstatic.com”,
host: “quests.armorgames.com”,
host: “r2—sn-nx57yn7s.googlevideo.com:443″,
host: “r6—sn-5uaeznze.googlevideo.com”,
host: “r6—sn-i3b7rnee.googlevideo.com”,
host: “r7—sn-jc47eu7l.googlevideo.com”,
host: “rc-regkeytool.appspot.com:443″,
host: “realtime.services.disqus.com”,
host: “s0.wp.com”,
host: “s1.dmcdn.net”,
host: “s1.hubimg.com”,
host: “s1.wp.com”,
host: “s2.dmcdn.net”,
host: “s2.wp.com”,
host: “s3-ec.buzzfed.com”,
host: “s3.hubimg.com”,
host: “s3.pimg.tw”,
host: “s7.pimg.tw”,
host: “s9.pimg.tw”,
host: “s9.thisnext.com”,
host: “s.cdn.gaiaonline.com”,
host: “s.gravatar.com”,
host: “s.pimg.tw”,
host: “sr.photos3.fotosearch.com”,
host: “s-static.ak.facebook.com”,
host: “static02-ec-vn.zalora.com”,
host: “static1.businessinsider.com”,
host: “static2.businessinsider.com”,
host: “static2.docstoccdn.com”,
host: “static3.businessinsider.com”,
host: “static4.businessinsider.com”,
host: “static5.businessinsider.com”,
host: “static6.businessinsider.com”,
host: “staticd.cdn.adblade.com”,
host: “static.exoclick.com”,
host: “static.libsyn.com”,
host: “static.linkbucks.com”,
host: “static.miniclipcdn.com”,
host: “static.movideo.com”,
host: “staticna2.lacoste.com”,
host: “static.payserve.com”,
host: “staticx2.dditscdn.com”,
host: “staticx3.dditscdn.com”,
host: “staticx4.dditscdn.com”,
host: “s.utdstc.com”,
host: “s.wordpress.org”,
host: “s.xe.com”,
host: “sync.graph.bluecava.com”,
host: “s.youtube.com”,
host: “t.6park.com”,
host: “tags.crwdcntrl.net”,
host: “th00.deviantart.net”,
host: “th01.deviantart.net”,
host: “th02.deviantart.net”,
host: “th03.deviantart.net”,
host: “th05.deviantart.net”,
host: “th06.deviantart.net”,
host: “th07.deviantart.net”,
host: “th08.deviantart.net”,
host: “th-th.facebook.com”,
host: “thumbs.3jizz.com”,
host: “ukcdn.usablenet.com”,
host: “use.typekit.com”,
host: “vdc-img-0.ig1-cdn.com”,
host: “video.ap.ntdtv.com”,
host: “wac.24ba.edgecastcdn.net”,
host: “wac.450f.edgecastcdn.net”,
host: “wac.76ff.edgecastcdn.net”,
host: “widgets.twimg.com”,
host: “wpc.a818.edgecastcdn.net”,
host: “wprp.zemanta.com”,
host: “www.open.com.hk”,
host: “www.secretchina.com”,
host: “www.stratfor.com”,
host: “www.youtube.com”,
host: “www.youtube-nocookie.com”,
host: “x.myspacecdn.com”,

Via Sucuri.net