Cisco ASA – Only Allow Mail Servers SMTP Outbound
KB ID 0000172 Problem It’s not unusual for nasty Virus’s and Malware once they have infected a machine, to set up outbound communications on the mail protocol SMTP (TCP Port 25), which can lead to your public address being blacklisted. So it’s considered good practice to stop all your clients getting mail access outbound through your firewall, while still allowing your mail server. Note: On Cisco firewall’s,...
Cisco ASA – Using ‘logging’ to see what ports are being blocked
KB ID 0000702 Problem If you look after a firewall, sooner or later something will fail, and the blame (rightly or wrongly), will be leveled at the firewall. I came back from holiday this week to find a client had got a problem with secure POP email. The problem had been fixed (temporarily) by dropping the affected users into a group, and opening all ports. As this had fixed the problem then it’s fair to say that the ASA was...
CentOS – Setup the iptables Firewall
KB ID 0000938 Problem I was a little perturbed to find out the firewall on my CentOS web server was wide open today. My server setup notes yielded no clues, so it was time to put my ‘Linux Head’ on and fix it. Solution 1. Connect to the server via console or SSH. As I’m going to change the iptables config file lets back it up (always assume you are going to smash something!) cp /etc/sysconfig/iptables iptables.bak 2....
Apple Device Stopped Sending Email – “Cannot Send Mail – A copy has been placed in your Outbox. The Recipient {name} was rejected by the server.”
KB ID 0000654 Problem Yesterday I got a text message from my wife to say she could not sent me an email. When she tried this happened: At first I thought it was just me, until I asked her to try sending an email to someone else, then she got the same result. Trying over 3G, and on the wireless at home, the results were the same. It had been working fine, but had then suddenly stopped working. My own iPhone was happily talking to the...