** Home security firm ADT's ADT.N shares up 3.1% premarket to $7.99 as co set to join S&P SmallCap 600 index .SPCY next week

** ADT to replace Arrowhead Pharmaceuticals ARWR.O in SPCY effective Mon, Feb 9, S&P Dow Jones Indices said late Weds

** ARWR migrating to the S&P MidCap 400 .IDX to replace Ciena CIEN.N

** Networking equipment maker CIEN elevating to the S&P 500 .SPX and replacing Dayforce as a result of software provider's acquisition by private equity firm Thoma Bravo

** For ADT, Stephens analyst Melissa Roberts cited in a note she expects passive funds will need to purchase about 69 mln shares, which equates to 10 days of implied buying demand

** Boca Raton, Florida-based ADT has ~819.7 mln shares outstanding for ~$6.4 bln market cap

** State Farm Insurance is top ADT holder with ~133.3 mln shares followed by Apollo Global Management APO.N (102 mln ) and index giant Vanguard (63.52 mln)

** Through Weds close, ADT shares off 4% YTD after 17% gain in 2025

** Of 5 analysts, 1 rates the stock "strong buy", 1 rates "buy" and 3 recommend "hold"; median PT $9 - LSEG

(Lance Tupper is a Reuters market analyst. The views expressed are his own)

((lance.tupper@tr.com 1-646-279-6380))