Tomasz Korwel
programmer, administrator, engineer - my everyday fights with reality

Mark passed. Still huge amount left…

Today suddenly my email server stopped accepting incoming connections. I wasn’t able to send any emails. After careful checking logs I have figured out that I’m a victim of DOS attack. More - I asked for it tuning maximum number of incoming connections in my firewall to low. Anyway, after correcting firewall I started to look over the internet how to better secure my Postfix configuration to prevent such problems in the future. What I have found is some simple main.cf tweaks posted on the nixCraft site:

disable_vrfy_command = yes
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks,
reject_non_fqdn_hostname,
reject_invalid_hostname,
permit

smtpd_recipient_restrictions =
permit_sasl_authenticated,
reject_invalid_hostname,
reject_non_fqdn_hostname,
reject_non_fqdn_sender,
reject_non_fqdn_recipient,
reject_unknown_sender_domain,
reject_unknown_recipient_domain,
permit_mynetworks,
reject_rbl_client list.dsbl.org,
reject_rbl_client sbl.spamhaus.org,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client dul.dnsbl.sorbs.net,
permit

smtpd_error_sleep_time = 1s
smtpd_soft_error_limit = 10
smtpd_hard_error_limit = 20

Simple as that, and it works. Now I can see how my server is rejecting spammers one by one without even talking to them past HELO command.

Technorati Tags: email server, DOS attack, Postfix

This country does not stop to amuse me. I’ve just bought an Internet Security software pack. I won’t mention the name because it’s not the case here. Anyway, the package cost $49.99 but the seller (software company?) offers $50 mail in rebate. So the question is - who makes money here? I bet on shipping company - it looks like it’s the only one who earn something (~$6.50) on that deal :-)

Technorati Tags: mail in rebate

It came today. Nice, red pepper Polar RS200 heart rate monitor. I have to admit that I was very curious waiting for it to see how my “usual” workout will turn out to be. The monitor itself is very intuitive and easy to use - it took me less than 5 minutes to have everything set up. Then I buckled up the wrist transmitter and started to walk.

Results were worse than bad. It turned out that after 15 minutes of walk my heart rate was constantly above 70%. Even more - 30 sec. fast walk (over 3 mph) elevates this level to well above 90%. Then at the end of the exercise 5 minutes very slow walk gave me only 72%.

Looks like we have very big problem here. There is literally long way to go before I will be able to say I’m fit.

Technorati Tags: Polar, heart rate monitor, Results

Our brand new snowboard carrier came this afternoon and I just came back from the garage after installing it on the White (our ZJ).

I have chosen Mount Blank 6 pair ski rack because it allows us to carry or two snowboards and two pair of ski from the friends of us who are usually going with us.

And as you can see above it was very good decision as 2 snowboards take more than half of space - I doubt I would be able to carry this set with 4 pair carrier. Finally we will be able to go with 4 people ski boots and some other supplies without stacking it all in the back and half of rear seat of our Jeep.

Technorati Tags: snowboard, carrier, Mount Blank, 6 pair ski rack