Crime-prevention experts in Japan are alerting residents to observable signs that indicate their homes may be targeted for burglary or fraud [1].

These warnings are critical because criminals use discreet communication systems to coordinate attacks. By recognizing these markers, families can implement preventive measures to reduce the risk of becoming victims of targeted crimes [1], [2].

Specialists have identified a practice known as "crime-marking," where symbols are placed on doors, mailboxes, or water meters to share information among accomplices [3]. These markings provide specific data about the residents and their habits. For example, the letter "W" may indicate that a woman lives in the home [3].

Time-based codes are also used to track when a property is unoccupied. A code such as "14→17E" signifies that a household is empty from 14:00 to 17:00 [3]. These markers allow criminals to time their entries with precision, minimizing the chance of encountering residents.

Beyond physical markings, experts warn that patterns of activity are monitored. This is particularly prevalent during long holiday periods. Some residents may face up to nine consecutive holidays during the year-end New Year period [4]. Police data indicates an increase in burglaries during the 2026 year-end holiday window [4].

Preventive measures include regularly checking the exterior of the home for unfamiliar marks, and maintaining a presence that suggests the house is occupied. Experts also warn that fraud is not limited to residential targets. An Impress Watch column author said, "Fraudulent 'transfer scams' targeting companies are occurring one after another, both domestically and internationally" [2].

Residents are encouraged to report any suspicious markings to local authorities immediately to disrupt the coordination of potential crimes [1].

“"W" may indicate that a woman lives in the home”

The use of 'crime-marking' reflects a systematic approach to urban crime where reconnaissance is shared among networks. By publicizing these codes, security experts aim to strip criminals of their primary advantage—information asymmetry—shifting the burden of surveillance from the perpetrator to the homeowner.