Home Network DNS Resolver

Raspberry Pi Kit
Scott Helme has a detailed procedure of how to configure Raspberry PI to act as a DNS resolver with DNS-level “content-blocking” for a network. It is a great weekend project, fun and useful. The hardware cost is around 100 CAD on Amazon.

Benefits

  • Content filter on DNS level, including ads and known nasty sites.
  • Reduced web traffic. Depends on sites you visit, but 40% is a reasonable expectation.
  • Upstream DNS queries are directed over https, so you get some extra privacy.
  • Pages load faster, take a look at the example.
  • Pi-Hole has a nice admin interface, so you get insight into DNS chatter on the network.

Here are network requests for a home page of a popular news site using default (no filtering) DNS resolver. In total it took 395 requests, 5.3 MB and six minutes to load.
Default DNS

Now if I switch to the DNS resolver on Raspberry PI:
DNS via pi-hole
Total of 143 request, 2.7MB to load, and 20.75 seconds. Take a look at all the lines in red with failed status, this is where the domain got blocked by the pi-hole on the Raspberry.

That’s ~ 50% less data and 17 times faster.

Continue reading “Home Network DNS Resolver”

Monkey Business

A challenge by Decision Management Community.

A zoo has four monkeys, during the monkey lunchtime each one ate a different fruit in their favourite resting place. Sam, who doesn’t like bananas, likes sitting on the grass. The monkey who sat on the rock ate the apple. The monkey who ate the pear didn’t sit on the tree branch. Anna sat by the stream but she didn’t eat the pear. Harriet didn’t sit on the tree branch. Mike doesn’t like oranges.

  1. What kind of fruit each monkey ate?
  2. Where their favourite resting place was?

So, how to solve this in SQL? It is easy to identify domains, predicates and rules; after that it is straightforward. Continue reading “Monkey Business”

Cyber Security Incident Scenario

This scenario has been designed to engage the entire cyber security incident response (IR) team and evolve the IR plan and capabilities as quickly as possible. It includes technical, managerial, financial, regulatory, legal, and public relation challenges.

Dante's Inferno

Take a look at your current IR plan and see if it stands up to this test. An organisation that does not have a cyber security IR plan, or a program, must act as if it has already been breached. If you do not have an IR plan get one; NIST SP 800-61 r2 is a good start. Continue reading “Cyber Security Incident Scenario”

Eight Years on SO

After eight years on StackOverflow and more than 600 answers, these are my favourite three.

  1. How to understand the fifth normal form? [🔗]
  2. Composite primary key vs. an additional ID column. [🔗]
  3. How to design this database to avoid the cyclic dependency? [🔗]

These are not the highest voted answers, but I like them. All three rely on basic time-tested knowledge and principles, favour simplicity and reasoning over confusion and technical trickery.