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perl hash slices are a way to access several elements of a hash simultaneously using a list of subscripts. It's more convenient than writing out the individual elements as a list of separate scalar values.

I recently needed to create a slice of a hash rather than a hash slice, ie. I wanted to create a hash with a subset of the key/value pairs from another hash.

Here's how I did it:

my %orginal = (foo => 'something', bar => 42, baz => 'king');
my %subset = map {$_ => $original{$_}} qw(foo bar));
# %subset is now: ( foo => 'something',  bar => 42 )

In my iptables configurations, I generally allow all traffic I am interested in and deny the rest, logging anything that is denied.

I found that this can get a bit noisy with loads of connections to udp:137 and udp:500, etc. so I decided to deny the more common ports without logging. But which are the most common ports?

Continue reading ‘Count of denied connections with iptables’ »