Relatively benign.
A compromised device inside the White House network could presumably be doing something _much_ worse than participating in a DDOS against random websites.
>> A compromised device inside the White House network
A whitehouse network. It isn't like everything done in that building run through a single wifi router. It is likely an unprotected network for personal use with zero connecting to anything important.
And it's right there in the second line of the article:
> One of the proxy services is a Russian company whose founder’s web hosting business was ground zero for cyberattacks against election systems in Arizona and Illinois in 2016.
Surely a Russian company known for cyberattacks against the US having direct access to the White House network is far more serious than just DDOSing random websites. This is espionage at the highest level. (Again.)