You only live once.

People are predictable. Language models know it.

Smart home defenses are tested

on random events.

Or on misuse cases a researcher had to imagine.

Introducing
Hϵlion
Home automation is natural. So predict it.
01Collect
02Schedule
03Predict

Ask real users.

40 users wrote 273 routines in plain English, plus hints about when each one runs.

USER-DRIVEN ROUTINE
IF the motion is detected
THEN turn the light bulb on
eveningmostly weekdaysfew times a day
<motion_sensor, motion, DETECTED><light_bulb, switch, ON>

Schedule a month.

Each user’s hints place their routines into hourly slots, giving one ordered, month-long event sequence.

INFORMED SCHEDULING · ONE DAY OF THE MONTH
0events in the HOME corpus

Predict what’s next.

An n-gram language model learns the patterns, then writes new scenarios one event at a time.

SCENARIO · 4-GRAM
HISTORYuser comes home
HISTORYit is evening
HISTORYgas range turns ON
PREDICTEDspeaker turns ON
PREDICTEDmotion is detected
PREDICTEDsecurity camera takes picture
LAST 3 EVENTS
up · most likely next eventdown · least likely, for stress tests
123 5710 n-gram order cross-entropy (bits)
6.9 bitsUNIGRAM
2.70 bitsBIGRAM
≈1.7 bitsn = 3 … 10
The HOME corpus is natural
≈0
bits of cross-entropy.

Lower than both English text and source code.

30,518events
273routines
40users

Valid to people. Useful to experts.

0%

“Strongly agree”

for up/4-gram routines, beating the 63.75% for users’ own routines.

0

Security & safety policies

specified from 27 unsafe scenarios, without imagining a single case.

0×

Less effort

than a graph-based baseline that can’t rank which event comes next.

Executed on real and virtual devices

Fewer than 10 scenarios. Three real flaws.

PLATFORM

Dropped actions

SmartThings sometimes skipped events, including locking the door.

PLATFORM

Zombie SmartApps

“Deleted” routines kept running in the background.

DEVICE

Unsafe auto-relock

A smart lock stayed unlocked after the door closed.

Towards a Natural Perspective of Smart Homes for Practical Security and Safety Analyses

Sunil Manandhar · Kevin Moran · Kaushal Kafle · Ruhao Tang · Denys Poshyvanyk · Adwait Nadkarni
S&P 2020 · IEEE Symposium on Security and Privacy