Do all these email bounces mean I have a bot infection?

How bots work

"Bots", short for "software robots", are programs that infect your machine and then are controlled remotely to perform various tasks that are at worst malicious and at least annoying.

The key thing to realize about bots is that they rarely know what machine they're on, and they rarely, if ever, try to impersonate the identity of the machines own.

They're just listening for and following instructions that they're sent over the internet from someone who's controlling a network of bots to do their bidding.

Most bots do send out spam, it's true. But again, a bot on your machine is typically not impersonating you and is not sending out email "as" you. Rather, the bot will have received a list of email addresses and contact info from the botnet controller and will use that to send spam and impersonate the "From:" line as it does so.

Even though it may be on your machine, most bots do not send email that looks like it came from you.

So those bounces are not likely to be the result of a bot.

Bounces: from people you know

If you have an online address book - say a contacts list in an email service like Hotmail, Gmail or others - and the bounces are coming back from email addresses that appear in that address book, then you probably have a completely different problem.

That account has been hacked into.

This probably has nothing to do with your computer at all. More likely, a hacker has somehow gained access to your email account ID and password and logged in as you. They may or may not have changed your password, but they're very likely to be sending out spam to all of your contacts while they have access to your account.

At this writing, I'd have to say this is the fastest growing form of spam and phishing attempted today.

Someone's sending email that looks like it's from me to my contacts, what can I do? covers the topic in more detail, but the short answer is: login to your account if you can and immediately change your password. Also, change all account recovery information that might otherwise allow a hacker to regain access by feigning a lost password.

If you can't login, take whatever account recovery steps that are available to you to regain access to your account as quickly as you can.

Bounces: from people you've never heard of

If the bounces that you're getting are from email accounts that you don't recognize, then ... well ...

You probably don't have a problem.

Seriously.

Your machine is probably not sending out spam and your email account has probably not been hacked.

There's nothing for you to do, because you don't have a problem.

The "problem" is that somewhere else, someone else is sending spam - perhaps a bot, perhaps something else - and that spam has your email address in the "From:" line. It's called "From spoofing" and it's trivial to do. It's also an exceptionally common way for spammers to further cloak their identities: they make the spam look like it's coming from someone it's not.

This is totally out of your control. There is nothing you can do, there is nothing for you to "fix".

Bounces: it's usually not related to your computer

There are exceptions, of course, but by and large, if you're experiencing a problem related to receiving excessive email bounces, then it's almost certainly not related to your computer.

Yes, you could certainly have a malware infection, but such an infection on your machine would not manifest as you receiving a lot of email bounces. It's more likely that you'd notice system slowness or unexpected internet usage. (Hopefully what you'd actually notice would be your anti-malware tools telling you that you have an infection. )

Getting a lot of email bounce messages is more likely either a sign of a hacked email account, which you should take steps to fix or common "From spoofing", which you can do nothing about.