Email is inherently a malicious traffic stream

It’s something many people don’t think about, but the majority of the traffic coming into the SMTP port is malicious. Spam is passively malicious, in that it just uses resources and bothers people. But there is a lot of actively malicious traffic coming into the SMTP port. Email is used as a vector to spread viruses and other malware. Email is also used for phishing and scamming. Many of the major hacks we’ve heard about over the last few years, including those in the email space, started with a single user getting infected through email.
We talk a lot about delivery here with clients and primarily focus on making sure their mail looks as unlike malicious mail as possible. We focus on spam filters, but every piece of mail goes through filters that also look for viruses, phishes, malware and other malicious traffic.
Mail servers are under attack constantly. The only reason our inboxes are useful is through the hard work of many people to filter out the bad and keep users from seeing the bulk of the mess attacking them.

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CNN warns about Target copy-cat phishes

Target did indeed do a blast to customers to offer one year of free credit monitoring. The problem is scammers are also on the prowl and are sending out similar emails.
Target even says it has identified and stopped at least 12 scams preying on consumers via email, Facebook and other outlets.CNN: Did you get an email from Target?

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The best time to send email

This subject comes up over and over again. Many senders are convinced clock_at_sign that there is a best time to send email. Countless research hours have been dedicated to finding that best time to send email. Numerous blog posts discuss what the best time to send email is.
From my perspective, there are better places for senders to spend time than figuring out what the exact right time is.But, senders still ask when the best time to send mail is.
There are a lot of reasons I can come up with as to why there’s no best time to send email. But the really big one is that when you send a mail has no impact on when it gets delivered.  There are multiple steps between hitting the send button and the mail being delivered to the inbox totally outside the control of the individual sender.
Email is designed as “store-and-forward.” This means there are potential delays at multiple steps inside the process.
Sending queues are called queues for a reason. Emails are sent out individually, particularly when an ESP uses VERP as part of its sending. There is actually a time overhead for making a connection to a recipient server and sending the email.
Receivers have queues, too. They can only accept so many incoming connections at a time. They have limited resources to accept all the mail their users want.
Receivers may delay mail between accepting it at the MX and delivering it to the inbox. This isn’t ideal and it’s not usual, but it can happen.
Recipients using IMAP accounts may not check mail regularly. They may only collect mail a few times a day.
These are only a few of the reasons that send time doesn’t necessarily equate with delivery time. Of course, 99% of the time email is mostly instantaneous. The internet is robust enough that a message sent is delivered seconds later. I see it happen all the time, when colleagues and I send email during calls. But, when mail fails, it sometimes fails spectacularly. Back in the dark ages (of the early 90s) I had an email that took almost a year to get to the recipients. Best I can tell, it got stuck somewhere in the depths of a machine in the middle of the university mail system. Eventually that system fell over and someone noticed and rebooted it (maybe it was walled up somewhere?).  The reboot shook my message out of where ever it was stuck.
 

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Compromising a Mail Client

Your entire work life is in your work mail client.
All the people you communicate with – co-workers, friends, family, vendors, customers, colleagues.
Every email you send. Every email you receive. Any files you attach or receive.
If someone can compromise your mail client, they can see all that.
They can save copies of all your emails, data-mine them and use them for whatever purpose they like. They can build a view of your social network, based on who you exchange emails with, and a model of who you are, based on what you talk about.
That companies like Google do this for “free”, advertising supported webmail shouldn’t be much of a surprise by now – but your corporate email system and your work email is secure, right?
What if an attacker were to set up a man-in-the-middle attack on your employees? Install malware on their iPhone, such that all traffic were transparently routed through a proxy server controlled by the attacker?
Or they could use a more email-centric approach, configuring the compromised mail client to fetch mail from an IMAP server controlled by the attacker that took the employees credentials and passed them through to their real corporate IMAP server – that would let the attacker completely control what the compromised user saw in their inbox. As well as being able to read all mail sent to that user, they could silently filter mail, they could deliver new mail to the users inbox directly, bypassing any mail filters or security. They could even modify the contents of email on-the-fly – adding tracking links, redirection URLs or injecting entirely new content into the message.
Similarly, the attacker could route all outbound mail through a man-in-the-middle smarthost that copied the users credentials and used them to send mail on to their real corporate smarthost. As well as being able to read and modify all mail sent the attacker could also use that access to send mail that masqueraded as coming from the user.
Sounds like the sort of thing you’d expect from criminal malware? Not quite. What I’ve just described is Intro, a new product from LinkedIn.
LinkedIn will be asking your users to click on a link to install a “security profile” to their iPhones. If they do, then LinkedIn will have total control over the phone, and will use that to inject their SMTP and IMAP proxies into your users mailstreams. The potential for abuse by LinkedIn themselves is bad enough – I’ve no doubt that they’ll be injecting adverts for themselves into the mailstream, and their whole business is based on monetizing information they acquire about employees and their employers. But LinkedIn have also been compromised in the past, with attackers stealing millions of LinkedIn user credentials – if they can’t protect their own users credentials, I wouldn’t trust them with your employees credentials.
You might want to monitor where your employees are logging in to your servers from – and suspend any accounts that log in from LinkedIn network space.
Edit: Bishop Fox has looked at Intro too, and come to similar conclusions. TechCrunch too.

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