Brief Update: Please note: I believe this only pertains to moderators of Yahoo Groups (this one and probably others).
The potentially malicious e-mails are no longer coming with the spoofed xl7/yahoogroups sender. You now need to check the full header [ideally in a safe environment]. For example, in several recent ones I found this:
X-Apparently-To: xl7-owner@yahoogroups.com
In many (possibly all) cases, the message is bounced by the yahoogroups server.
Off topic (but probably related): on my personal phone, I have noticed an increase in spam/spoofed calls seeming to come from a phone number that is one digit off from my phone number (almost always the last digit) and usually with a different area code.
Sad to say, but cyberwars is very real. To me it is mind boggling that a company like Yahoo, with all of it's technological resources, can't stop potentially malicious communication from being bounced back to moderators. Perhaps they found a way or preventing the e-mail with the previous strategy the cyberwarriors were using. That might explain why the mail is being sent with different senders than the others.
Anyhow, it seems that members are still being protected.
Steve