Na Linode, estamos extremamente orgulhosos das nossas equipas de Apoio ao Cliente e Confiança & Segurança e do trabalho que fazem em conjunto - são equipas chefiadas por humanos reais que partilham um objectivo importante: manter a nossa plataforma segura e livre de abusos e fraudes, e elaborar políticas que mantenham os nossos clientes seguros. Isto significa que quando se envia um e-mail para email@example.com, pode-se esperar ouvir, geralmente em minutos, de uma pessoa real - um membro de toda uma equipa que passou por uma extensa formação para compreender todas as complexidades que podem advir do tratamento de abusos, e que pode responder a relatórios com empatia e urgência.
Um dos problemas mais comuns para as nossas equipes (e para a nossa indústria) é o abuso de e-mails de spam. Constitui uma parte significativa dos problemas que a nossa equipe de Confiança & Segurança tem de resolver, e é um problema que se torna cada vez mais difícil de resolver à medida que os utilizadores fraudulentos se adaptam a novos métodos de paragem e bloqueio de abusos. Com o crescimento da Linode, refletimos sobre o que podemos fazer para dissuadir spammers e usuários fraudulentos de usar nossa plataforma.
Em resposta a este problema, a partir de hoje, Linodes em contas de clientes recentemente criadas terão ligações de saída dos portos 25, 465, e 587 restringidas por defeito. Esta alteração apenas afecta os clientes que se inscrevam a partir de hoje - se já for cliente Linode, não serão feitas alterações a quaisquer Linodes existentes ou novos Linodes.
A restrição do acesso a estas portas, que são utilizadas para a entrega de correio através de SMTP, contribuirá em muito para reduzir a quantidade de spam transmitido a partir da nossa plataforma. Contudo, também reconhecemos que muitos clientes têm uma necessidade legítima de enviar correio, e queremos ajudá-los a fazer isso. Para esses clientes, o processo para remover estas restrições é simples:
- Configurar registos A válidos e DNS invertido para os Linodes que gostaria de utilizar para o envio.
- Abrir um ticket de Suporte e fornecer-nos alguma informação básica (a informação que pediremos está delineada no nosso guia "Running a Mail Server").
A nossa equipa de Apoio irá rever o seu pedido - se tudo parecer bem, eles irão remover as restrições do porto SMTP para que possa começar a trabalhar.
Ao implementar esta nova política, o nosso objectivo é equilibrar a necessidade de manter a nossa plataforma segura com o entendimento de que muitos dos nossos clientes têm necessidades legítimas de enviar correio. Queremos que Linode seja a melhor plataforma de nuvem para os programadores e os clientes para quem eles constroem. Ao manter os maus agentes de fora e o nosso espaço IP livre de spam e abusos, esperamos entregar-lhe uma experiência de nuvem mais limpa, mais eficiente e, em última análise, melhor para si.
There’s a confusing discrepancy between this article and the “Running a Mail Server” guide. Here is saying connections to (INCOMING) those ports will be blocked. The guide says OUTBOUND connections will be blocked.
Which is it?
The former makes more sense as it helps stop accidental mail servers on the network. The later doesn’t as it prevent sites/servers from sending emails to administrators. (Like logcheck, update notices for websites, etc.)
Hey Paul. I’ve just updated the post – we block outbound connections on those ports, not inbound connections.
Hi, I don’t understand how this works. I am running OpenVPN on my Linode and when I use it, I can’t email out from thunderbird. Can you explain how I can allow the connections? Because none of this makes sense unless I was using a domain/email
Next step, let ML algorithm decide who to unblock? Anyway, very stupid decision. Customers pay you money. You’re a commodity interchangeable service. If you make stupid additional barriers for customers, they will just live to your rivals. Nobody wants to wait and talk to your support, justify himself and be dependent on someone’s will.
Thank you for sharing your thoughts with us. This policy was created out of a need to address abuse on our platform in a comprehensive way, and we carefully weighed this against industry practices. We are, and always will be, a team of real humans, and we will respond to every request.
If you would like to reach out to us immediately to address these concerns on your account, we are available 24/7 via phone. https://www.linode.com/contact
Can I suggest that moving your main site to Cloudflare may not look the best to some from an anti-spam (and anti-abuse in general) perspective, and perhaps could also suggest to others a possible lack of confidence in your infrastructure’s ability to handle your site’s traffic by itself?
Or could it be in part because your new site has a significantly large bandwidth usage and they help you with the static content bandwidth?
Spammers send mail, that is, make outgoing connections to other mail servers, so I’m not sure how blocking incoming connections helps.
Hey Kenyon. Just updated the post to clarify – we block connections *from* Linodes (e.g. outbound connections), not inbound. Sorry for the confusion!
Ah, but mail servers don’t usually make outgoing connections to ports 465/587…mail client apps do.
I think I understand the change, having seen quite a few SMTP bruteforce attempts in my own mailserver’s logs, but it still doesn’t entirely *fit* the explanation provided.
I think that for many users an intermediate unlock level where 465/587 are allowed but 25 is still blocked would make sense, e.g. if they’re not running a mail server at all but just want to use msmtp for relaying Cron mail through Gmail, or using Amazon SES, or such.
That’s an interesting idea and something we can consider as we review the implications of this change. I appreciate you taking the time to share your thoughts on how to better serve legitimate users. I’ve shared your thoughts with the rest of the company to review.
Port 587 should not be blocked, this port is not used for receiving unauthenticated mail and was created specifically to allow authenticated mail from senders so that networks can block port 25 for non-mail-server traffic.
To be clear, port 587 cannot be used to send spam.
While most mail servers ask for authentication, port 587 can be used as a way to send spam. Port 587 is often used for outgoing unencrypted mail from an SMTP server, and is why we’ve chosen to include it in these ports that are initially blocked.
Good move (both actions), if it helps Linode users running legitimate mail servers getting their non-spam mail accepted on the internet. This has been a problem in the past; also due to other actors (e.g. Google) being entirely non-transparent about how they decide to drop your mail.
When you say we need a valid A record, does that mean we have to use your DNS service in order for the ports to be unblocked? What if we use DNS servers provided by our registrar, a third party, or even a server we operate? Will there be any accommodations for those customers?
You’ll still be able to use whichever DNS servers you like. We can verify valid records using commands like
digin order to validate requests to unblock mail ports. More information about using
digcan be found via this link.
I am curious how do you plan to work this for setups where servers come up and down frequently but have a need to send email when done? Is this going to be an account wide approval or per machine approval?
What is going to be the SLA for response on these requests?
Account wide approval can be done by opening a Support ticket. We work to get to these requests quickly, but if the request is urgent, it’s best to reach us by phone.
I am an existing customer. If I understand correctly I can still provision a new server and not have to contact support to get it unblocked?
Yes, that’s correct! Existing customers do not have to contact support, as mail ports are not blocked by default for them.
Oh cool. I’m sure people are going to be happy to reach out to support immediately after creating an account and waiting hours to actually have full access to the services they’ve paid for.
Such a useless change that will undoubtedly be followed by more. How long until each Linode requires justification?
Hi James! Between actively looking for tickets related to these SMTP restrictions and our 24/7 phone support, we’re able to grab most requests fairly quickly. And I can definitively say that we have no plans to require justification for each new Linode 🙂
Based on what I see in my servers logs, only one way to fight with spam and attack attempts originated from Linode subnets is to block traffic from them. There is no day without attempts:
220.127.116.11 – – [05/Dec/2019:19:28:52 +0000] “GET /api/v1/pods HTTP/1.1” 403 341 “-” “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36”
18.104.22.168 – – [05/Dec/2019:23:46:37 +0000] “GET /msdn.cpp HTTP/1.1” 400 345 “-” “WinHTTP/1.1”
Hey there — our Trust & Safety team has determined that the IP addresses you’re reporting are currently operated by security researchers, and that the associated traffic isn’t intended to be malicious.
Apart from blocking traffic originating from us, we’d gladly pass blacklist requests for your own IP addresses on to our customers — just send the requests to us at firstname.lastname@example.org along with the information you’ve posted here. We monitor this email 24/7, so you can also report any other malicious activity you see coming from our platform there and we’ll quickly investigate.
I feel that this is a good approach, however, those that do have an SMTP server might now know the best ways to fight spam.
Perhaps it would help to have a linked document on best practices, or considerations to keep in mind, emphasising stuff like…
– Establishing and maintaining a secure password policy for e-mail accounts (so passwords can not be ‘123456’ or ‘password’, and some other dumb ones)
– Having an outgoing filter might avoid spam/malware distribution (ie. SpamAssassin, MailScanner, or cloud services like SpamExperts, MailChannels)
– Preventing users from redirecting their inbox to free e-mail providers (or any at all) will also stop spam distribution. Most of these services provide POP/IMAP import which is by far superior to a forwarder
– Enforcing SPF / DKIM on your domains, and outgoing SMTP server. This will make it harder for people to use your domains for phishing, but also will prevent your own server from sending e-mail thru domains you don’t own.
– Setup your SMTP server to reject outgoing e-mail when it belongs to an e-mail address that you don’t own (ie. don’t allow your servers to send e-mail personifying someone else)
– Always use SSL, everywhere, self-signed or free certificates are OK, but not recommended.
Those are all great points. Thank you for outlining them for people. Linode has a few different email server guides that walk the user through setting things up properly. In particular, the Configure Spam and Virus Protection section of the Running a Mail Server guide, which is linked in the post above. This section goes over a few of the things you’ve mentioned. I can definitely see how helpful it would be to have all of this information in one place. So, I’ve passed your suggestions along to our documentation team for consideration. ?
It would be better if Linode default whitelist certain well-known 3rd party SMTP gateways. For example “email-smtp.us-west-2.amazonaws.com:587” for Amazon SES service.
I mainly use Amazon SES for email because of reliability. After I moved my website to linode, I found that all the email can’t be send because Linode blocked my server connect to Amazon SES gateway. Now I have to open a ticket and wait for unblock, not a smooth experience overall.
I’m sorry to hear that you experienced some frustration with this process. We are constantly looking for ways to improve this procedure, and we really appreciate you sharing your thoughts with us. I can definitely understand the validity of your point, so, I’ve passed it along to our team for further consideration.
Please, feel free to share any thoughts you may have about any of our services by sending an email to email@example.com.