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Interpreting Scan Results — Linux Machines

On most Linux machines, the following ports will be open:

TCP Port	UDP Port	Service	Notes
22	22	Secure shell	A more secure way of connecting to the machine, like an updated telnet session.
901	901	SAMBA Web administration tool	SAMBA Web Administration Tool http://www.samba.org/samba/ docs/man/swat.8.html

If the machine is a server, the following ports may be open:

TCP Port	UDP Port	Service	Notes
21	21	FTP	File Transfer Protocol. Disable if not needed. Also, disable anonymous FTP if not needed. MOREnet Security recommends SFTP instead of plain FTP to the traffic is encrypted.
25	25	SMTP	Simple Mail Transfer Protocol. Should be enabled on a server but not on a workstation.
53	53	DNS	Domain Name System. Used only if a site is running its own DNS server. If not running a DNS server, stop this service and use MOREnet's DNS servers.
80	80	HTTP	HyperText Transfer Protocol. Webserver; things like Apache, Microsoft's Internet Information Server, etc.
110	110	POP3	Post Office Protocol, version 3. Used to POP mail from the machine.
8080	8080	HTTP Proxy	There are many examples of proxy servers running on this port.

This is not a complete list of ports and services. Your server may have other ports open. For a complete list of ports and associated services, please see one of these locations:

Best Practices for Network Security

Don't run unnecessary services.
Keep software up to date, with respect to security issues.
Restrict access to services via authentication, filters and encryption.
Monitor access logs.
Properly install and monitor "personal firewall" to detect and contain both incoming and outgoing traffic.
Properly install and monitor external firewall as an added layer of protection.

Security Information

2007 Advanced Technical Security Symposium
Security Series Web Seminars
Security Awareness

Services

Blackhole DNS
E-mail Virus and Spam Filtering
Good Net Neighbor Service - Phase 1
Good Net Neighbor Service - Phase 2
Internet Content Filtering
Remote Vulnerability Assessment Service

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Incident Response
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Security Policies and Presentations

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E-mail: security@more.net
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