When last we checked in with Malibu Media (owner of a library of adult films and associated copyrights), Malibu had filed suit against John Doe and then used the Court's subpoena power to take an IP address which identified an alleged infringer's network connection and force the ISP to identify which subscriber belonged to that IP address.  (The Electronic Frontier Foundation has written about Malibu Media here.)

In another case, a little further down the enforcement timeline, Malibu Media had received from the ISP the subscriber's identity. But instead of suing the subscriber, Malibu Media sued the subscriber's son:

The ISP, Bright House Networks Online Service, identified [Father] as the internet subscriber...Upon investigation, Plaintiff learned that [Father] lives with his son...

At the time this case was originally filled, Plaintiff knew only that the infringer was using the internet subscriber's IP address.  Usually, the subscriber is the infringer.  But, as is the case here, sometimes the infringer is another person residing with the the subscriber, who the subscriber has authorized to use the subscriber's internet.

Time timespan of infringing activity precludes the possibility that the infringer was a short term guest or other interloper.

Plaintiff's Amended Complaint [Dkt. 8] at 5.  Malibu then goes on to explain that it found other video files downloaded by the IP address (for tv shows like Breaking Bad, Lost, Weeds, and Futurama) and that the Son had "liked" these tv shows on Facebook.  Thus:

...[Son] is the most likely person to have used BitTorrent in the house from where the infringement emanated.  Consequently, Defendant is the most likely person to have infringed Plaintiff's copyrighted works through the use of BitTorrent.

Plaintiff's Amended Complaint [Dkt. 8] at 6-7.

So, after being served, [Son] sought dismissal, explaining that [Son] did not reside in the home during the time of alleged infringement and attacked Malibu's infringement evidence as stemming from an unlicensed investigator on a contingency pay arrangement.

[Son] also explained a decision by Judge Ungaro in the Southern District that [Son] described as a "game changer" for thwarting Malibu's activities:

Plaintiff has not shown how this geolocation software can establish the identity of the Defendant.  There is nothing that links the IP address location to the identity of the person actually downloading and viewing Plaintiff's videos, and establishing whether that person lives in this district.....

Even if this IP address is located within a residence, the geolocation software cannot identify who has access to that residence's computer and who would actually be using it to infringe Plaintiff's copyright.

Malibu Media v. Doe, Case No. 1:14-CV-20213 (S.D. Fla. Mar. 5, 2014) (J. Ungaro).  Returning to the present case, Judge Moody was not persuaded by the Southern District's reasoning:

While it may be true that the IP subscriber, or the son of an IP subscriber as it is in this instance, is not undoubtedly the infringing individual, the Plaintiff's burden at this stage is only to demonstrate plausibility.  See [Ashcroft v.] Iqbal,556 U.S. 662, 678-79 (2009); cf., Malibu Media LLC v. John Does 1-16, 902 F. Supp. 2d 690, 698 (E.D. Pa. 2012) ("The Court acknowledges, however, that the information provided by the ISPs in response to the subpoenas will not necessarily reveal the identities of the actual infringers, but may, with other discovery, lead to the infringer's identities.")  To that end, Plaintiff has alleged a plausible link between the subscriber assigned to [the IP address], Defendant, and the copyright infringement, and any factual disputes are inappropriate at this stage.

As to the charge that the investigator's technique's were inappropriate, the Court found those allegations premature.

Motion to dismiss, denied.

Malibu Media, LLC v. [Son], 8:13-cv-3007 (M.D. Fla. Aug. 1, 2014) (J. Moody)