poor 802.11ac router design

 My advice to WiFi router manufactures: If you can not provide high-performance gigabit ports on the LAN side and WAN side, do not attempt to put your 802.11ac wireless router in the market. It is just a waste of time, money and technology. The one I give below is a piece of shit !


450 Mbps LTE download speed

If a mobile carrier has 20 MHz bandwidth in each of the 1.8 GHz, 2.1 GHz and 2.5 GHz bands, it can offer 450 Mbps download speed by Carrier Aggregation across different bands in LTE-A network. Any such resourceful carriers in the world?



PC 21276 殘害和平表達素求及手無寸鐵嘅公民,證據確鑿,惡警犯法,罪加一等!


IT Voice 之恥

IT Voice 之恥,你去死啦!


Chrome flash plugin

Google makes Chrome a piece of shit by embedding its own flash plugin into the browser which crashes with Adobe plugin. Chrome does not know which one to use !  I need to manually disable the embedded one.  





RFC 1918 address leaked out

What the hell is that?
[localhost~]# dig a +short mail.hkbn.com.hk

RFC1918 address leaked out ? Misconfiguration ? Or an authoritative name server serving both Intranet and Internet ?


.xxx generic top level domains

Whether you like it or not, ".xxx" triple x top level domain has been in services for over 2 years. Of course, it is for pornographic websites only. I like the idea because only a simple filtering mechanism can be used to ban children from accessing adult websites.


DNS reply larger than 4096 bytes

I thought I would never be able to generate a DNS query with reply size larger than 4096 bytes. I was wrong ! Just look at this.

[warren@dnssec ~]# dig any doc.gov | grep SIZE
;; MSG SIZE rcvd: 9735

Of course, the reply has to fallback to TCP instead of UDP. Thanks to US Department of Commerce for letting me to play around with this.

Hackers, don't use this for amplification attacks.  You will fail.


Q1 2014 DDoS Attack Report

Thanks to Prolexic (part of Akamai) for sending me this Q1 2014 DDoS Attack Report. I love this more than Akamai's State of the Internet Quarterly Report.

Fuck you, China and USA for generating 40 % of world's attack traffic.


Historical heartbleed vulnerability

I need to make myself more competent on Openssl and TLS after the discovery of this historical Heartbleed Bug. I hate to learn and practise again but there is no shortcut.


heartbleed bug

Announcement : If network administrators have difficulty to check whether their SSL private keys are affected by the heartbleed vulnerability, they can send me an email attaching the keys and let me know the websites. I will check for them, free of charge, of course.


VPN for my mobile phone

不要再懶,起番個VPN 比自己手機在大陸番牆上 facebook, 雖然手提電腦可以用SSH + Proxy Server, 始终都覺得不夠用.


home routers as open resolvers

A friendly note to home users with broadband routers : Quite a large number of home routers in use for years have open resolver fault. Please go to 


check your router status and upgrade the firmware to plug the hole.
By having your router as an open resolver, you are helping cybercriminals to launch DDoS attacks.

This is evidence of ASUS RT-N66U routers able to do DNS amplification attacks.


Open resolvers again

I repeat my statement again: Don’t compare open resolvers with Google Public DNS ( and and OpenDNS, they are not the same.  Google and OpenDNS have all sorts of security features that are beyond imaginations. 


No more Amplification Attack

For God's sake, please disable "monitor" if you operate publicly accessible NTP servers.

By the way, if monitor can be removed from the latest patches of NTP daemon, I see hope of disallowing "ANY" query in resolvers in coming patches.  All name query should be specific.   If you want to do mail exchange, ask for MX followed by A record.  If you want to know the authoritative name server of a domain name, ask for NS.  These days, "ANY" would not serve any purpose except network attacks.



Another interesting stuff. An IT guy try to ping in an attempt to troubleshoot connectivity problem. He should be fired immediately.


MAC address intrusion

A complainant said his home PC was accessing by other people over the Internet through MAC address intrusion.  The complainant sought help from his serving ISP.  What should the ISP do?  Just laugh and do nothing. 


Boosting WiFi signal strength by a Coke can

In today's Apple Daily News, there was a story about boosting WiFi receiving signal strength by means of placing a Coke can close to an antenna.  A picture is given below.

The distance between the aluminium foil and the whip antenna should be carefully calculated in order to maximize the directivity which as a norm is λ/2. For this TP-LINK 2.4 GHz router, the distance is (3x10^8/(2.4x10^9x2) = 0.0625 meter or 2.5 inches.


IPv4 turn-off day in 2014

In order to show the technical maturity of IPv6, some intelligent people have suggested to set aside one day in 2014 as the IPv4 turn-off day.  I just want to ask if this idea really makes sense.  If turning off IPv4 results in a large number of users have difficulty  in accessing major websites, people will have a very bad idea about the quality of IPv6. I certainly agree there needs to be an IPv4 turn-off day to test where we are during the transition process and whether there will be broken applications if relying on IPv6 alone. The timing is not this year. It might be in the next 10 years.  For the time being, just enable dual-stack and stay with dual-stack as much as possible.