No one wants to be associated with a website domain or web hosting service (including WordPress hosting) that is prevalent to being hijacked to send spam, and most businesses will factor this into their web hosting provider decisions automatically.
In the US, companies have another reason to ensure they are not caught up in spamming. The University of Texas at Austin have started a new initiative to “name and shame” the names and domain names of businesses and organisations that appear as major sources of spam emails, in the hope that the adverse publicity will put pressure on them to up their security measures to avoid the problem in the future.
Poor security measures on the part of the business or their hosting provider can lead to botnets being used to send spam emails from the email servers of the affected company without their knowledge.
Whilst there is little concrete data on the effect being a spammer (even inadvertently) has on a companies’ business, no one can be under any illusion that it is a good thing. If spam email can be sent, then other data such as credit cards and addresses can also potentially be compromised, as Sony has found to its cost recently.
The initial rankings are sourced from correlations of groups of IP addresses to organisations and businesses by internet security research firm Team Cymru, and the University are seeking responses from businesses affected. European businesses are likely to be less impacted by the list right now, but spam is a worldwide problem, so no one can, or should rest on their laurels.