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Skåne Sjælland Linux User Group - http://www.sslug.dk Home   Subscribe   Mail Archive   Forum   Calendar   Search
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BOF om spam - resume



Her er hvad der kom op på tavlen. Lempeligt fortolket af undertegnede.

Afsenders IP#
		220 OK
		HELO foo.dk (eller EHLO foo.dk)
		250 OK
SMTP		MAIL FROM: <sslug@sslug>
Envelope	250 OK
		RCPT TO: <sslug@sslug>
		250 OK
		DATA
		354 End with '.'
Mail headers	Received from .....
		Subject: Hej
		From: <sslug@sslug>
		To: <sslug@sslug>

Mail body	Hej
		.
		250 OK
		QUIT
		221 Bye

Ide til at spare båndbredde:
	Modtag til og med mail headers.
	Analyser mail-headers
	Hvis ikke OK: Klip forbindelsen og blacklist afsenderen ala RBL

{} = 0 falske afvisninger
[] = få falske afvisninger

[viruskiller] {egen database}
{ormekiller}

Greylisting
	{http://greylisting.org/  - Midlertidig afvisning (fejl 4xx)}

Spam fingerprinting
	{egen base}
HELO
	{hvis afsender udgiver sig for at være dig selv}
Filtre:
	Regelbaserede
		SpamAssassin http://eu.spamassassin.org/index.html
	Statistiske
		dspam http://www.nuclearelephant.com/projects/dspam/
		CRM114 http://crm114.sourceforge.net/

Blacklist (RBL)
	Problematisk hvis ikke kender politikken for at komme på
	Brug flere: Hvis 3 siger det samme, så afvis
Whitelist af server
Score based
	Kombination hvor flere af reglerne giver point.
	Alle over en vis grænse behandles som spam
Check afsender
	Se om afsender adressens mail-server vil acceptere en bounce
Digital signatur
	Hvem skal være udsteder?
Web of trust - ala PGP
	Hvis du er min ven, så får du 1 spampoint
	Hvis du er min vens ven, får du 2
	Hvis du er min vens vens ven, får du 3
SPF	
	http://spf.pobox.com/
	Problemer ved forwarding og email-lister

Human challenge
	Problem hvis begge benytter human challenge
	Kræver ekstra persontid
Betaling per email
	Hvordan skal betaling styres?
	Hvad med email-lister?
	Betaling med CPU-tid => spammer køber større maskine
Generelt problem: Hvis en løsning kræver at hovedparten af alle er med
så virker løsningen ikke i praksis.


Web bug
	http://en.wikipedia.org/wiki/Web_bug

/Ole
-- 
Et billede siger lige så meget som 3 bogstaver
  -- Christian Jul (om PDF-logo)


 
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