Self-theft of the meter: It consists of the user subtracting his meter permanently, pretending that it was stolen. Because in some places the theft of meters is really massive, it is extremely difficult to distinguish self-theft from real theft.

Theft of the register: It consists of extracting the register, leaving the cast. It occurs frequently if the meter is anchored on the floor.

Vandalization: It consists in destroying the meter, hitting it, affecting its operation or avoiding the reading (Figure 1, A).

Scratching or painting of the glass: This form allows the meter to work, but prevents it from being read.

Perforation of the glass: It consists of drilling a hole in the glass to access the register to destroy it or to temporarily introduce objects that paralyze the consumption count (Figure 1, B).

Drilling of register from the side: It is similar to the previous form of tampering, but with the difference that it is done from the sides with a hot metal object or with drills. It is more difficult to detect at the time of reading.

Perforation of the turbine cast: Meter models with plastic casts can be perforated with hot metal objects to access the helices, at points that are not visible to the reader, being able to paralyze them temporarily or permanently, without taking out the meter. Although metallic casts could also be perforated (with a drill), it is much more difficult, exposes the tamperer to be discovered and it is almost impossible to perform it at an invisible point.

Internal alteration of the helices: It consists of disassembling the meter to modify the turbine helices so that they move at a slower speed (Figure 1, G).

Alteration of the transmission mechanism of the turbine to the register: The magnetic transmission is interrupted or stopped with the introduction of small objects, such as metal or plastic tokens, between the turbine and the register (Figure 1, F).

Internal alteration of the gears of the register: It consists of removing the register from the meter and removing teeth from the different gears, thus causing the recorded consumption to be lower, depending on the percentage of the teeth removed (Figure 1, E) .

Paralysis of the helices: It consists of paralyzing the helices by introducing pins or glue from the entrance or exit of the water (Figure 1, D), previously uninstalling the meter.

Boiling the meter: It consists of uninstalling the meter and heating it so that its plastic parts deform or melt, altering or paralyzing the registration (^{Goodwin, Kaggwa, & Malebo, 2013}).

Meter reversal: The meter is turned over so that instead of increasing, the reading decreases as consumption continues.

Temporary removal of the meter: In periods of high consumption, the meter is removed or replaced by a “phantom meter”; after this period, it is reinstalled.

Temporary separation of the register: It consists of removing only the register from the meter, but not the complete meter, and putting it back before reading dates (Figure 1, C).

Reverse reading: in this case a pressurized air flow is used to reverse the register. To do this, the meter is removed, the register is revered and it is reinstalled.

Inclination of the meter: Some users tip the meter to one side to under-register, although, depending on the model of the meter, the effect of this is little, not reaching 10% of under-registration in most meters, that is, it is still registered 90% of consumption (^{Arregui, Cabrera, Cobacho, & García-Serra, 2005}).

Temporary introduction of wires: It consists of a wire being introduced from the property, without being able to see the tamperer in the act of tampering. It also allows regulating the consumption record so that it does not go to zero, avoiding suspicion. In addition, the wire can be removed on reading dates.

Temporary application of magnets: The magnetic transmission from the turbine to the register is braked with powerful magnets. They are applied to the side of the meter, from where they can be quickly removed, which makes detection difficult (Figure 1, H).

Depending on the regulations, the violation of security seals can be sanctioned as an infraction or crime.

Even if a broken seal is not accepted as evidence, it may result in the meter review or the application of other measures.

The visible presence of the seals or other indicative measure may be dissuasive for a user tempted to tamper his meter.

Vulnerabilities where indicative measures may show that a specific vulnerability was exploited to tamper the meter.

Vulnerabilities that do not require indicative measures.

Vulnerabilities where it is impossible to take indicative measures.

Against the possibility of perforating the register from the side (Vulnerability 2): Although there are no security seals for this, there is an indicative measure that consists of filling the meter box with expansive foam and taking a picture of the box (Figure 3, A). Since this foam always forms unique patterns, it is impossible to return it to its previous state once the meter has been tampered. Otherwise, it can only be detected by carefully checking the meter for which it is often necessary to uninstall it.

Against the possibility of perforating the cast (Vulnerability 3): There are no seals for this, the expansive foam method being equally effective to indicate this type of tampering.

Against the withdrawal of the meter (Vulnerability 4): There are several methods in use, such as the expansive foam and a seal that secures the locknuts that fix the meter (Figure 3, C). The latter allows the meter to be removed only after breaking the seal that cannot be replaced without leaving evidence. A third method is with the use of sealing wire, secured with a seal (Figure 3, B). For the reader to realize it is necessary to move the wire because the cut part can be glued or hidden so that it is not noticed (^{Ríos, 2013}).

Against the removal of the register (Vulnerability 5): The main use of security seals with wire sealant is to avoid the removal of the register. They serve to detect if the register was separated from the meter, which, even if the fact that the seal is broken cannot be sanctioned, is useful to realize that it is necessary to disassemble the meter and check if helices, gears, etc. were altered. Likewise, filling the meter box with expansive foam could provide evidence.

Against the inclination of the meter (Vulnerability 6): An inclined meter cannot be easily detected, when the user, before the reading date, returns the meter to its normal position. For this form of tampering the seal on the locknut is not useful (Figure 3, C), but two other measures:

The installation of security seals that serves to identify if the meter was uninstalled. For this it is necessary that the sealing wire, which fixes the security seal, is firmly attached so that the meter can be moved only after the wire has been cut or the seal has been broken.

The filling of the box with expansive foam.

Against the use of magnets (Vulnerability 8): A measure is the use of magnetism indicator seals. They are placed in the same meter and if they are subjected to magnetism they irreversibly indicate that there was a magnet nearby (Figure 3, G and H).

Against the vulnerability of the glass (Vulnerability 1): The destruction or perforation of the glass is self-evident at the time of reading, although perforations of diameters smaller than one millimeter have been found, which are difficult to detect.

Against the accessibility to the turbine through the tube (Vulnerability 7): A measure has not been found that evidences that the meter has been tampered, by introducing a paralyzing object from the site, this is without touching the meter. However, there is a preventive measure consisting of an anti-wire device (see below).

The serial numbers of the seals must be registered, associated with the meter and be accessible to inspectors and readers in order to be verified. It has been observed that many utilities in Peru do not proceed in this way, allowing replacing the broken seal with another, without being detected.

Lead seals (Figure 3, E), do not provide much security because they are easy to handle with cuts or heat, imitable or artificially aged so that they are taken as originals (^{Ríos, 2013}).

The security seals should preferably be transparent so that a possible tampering inside can be noticed.

Seals that are multi-body (such as male and female) must have the numbering on all parts or be physically attached, so as not to allow the removal and replacement of a part, for example, with stolen parts of seals from other meters (Figure 3, D; the seal is numbered in its 2 parts that were also joined).

One of the ways to violate plastic seals is with the use of heat that allows the removal of apparently fixed parts. Therefore it is recommended that they have heat indicators (Figure 3, F).

Get more sensitive indicator stamps. We do not know if these exist in the market.

Use seals on opposite sides of the meter. To be effective they must react to magnetism at a minimum distance of 4 to 5 centimeters (according to the diameter of the meter).

Place the seals in the middle of the glass. For this they must be adhered in such a way that it is impossible to be removed without leaving a trace (like the one in Figure 3, H).

Measures that have already been incorporated into the design. This mainly refers to meters observed in Peru.

Measures that are technically feasible to incorporate. It refers to measures that have not been observed, but which theoretically could be part of the meters.

Measures that are not technically feasible to incorporate.

Against the perforation of the register from the side (Vulnerability 2): Some meter models have, between the plastic housing of the register and the register itself, a metal tape, which prevents it from being perforated with hot pointed objects.

Against the possibility of perforating the cast (Vulnerability 3): The vast majority of meter models have a metal cast that prevents it from being perforated with hot pointed objects. In those with a plastic cast, no metal tapes or plates equivalent to those mentioned above have been found.

Against the withdrawal of the meter (Vulnerability 4): There are meters that have differentiated input and output threads, making it impossible to invert them. However, they are vulnerable against forms of tampering that involve the removal of the meter (reversal etc.). Therefore it is not an important advantage.

Against the withdrawal of the register (Vulnerability 5): Almost all meters allow the removal of the register, but only by breaking some type of security seal. However, it has been found that several models allow the register to be opened in such a way that the seal remains intact. Apart from that, a model has been found whose register is fixed with screws that can only be removed with violence or with a special key (^{González, Val, Rocha, & Segundo, 2010}).

Against the use of magnets (Vulnerability 8): Many meters have been provided with antimagnetic shields, consisting of nickel and iron alloy rings (Figure 4).

Against the vulnerability of the glass (Vulnerability 1): The glass of the meter is vulnerable due to the fact that it is manufactured with materials that are easily scratched, perforated or destroyed. It is feasible that they can be replaced by high-resistant transparent materials, such as metal glass.

Against the accessibility of the turbine through the tube (Vulnerability 7): An anti-wire device can be fixed at the meter outlet to prevent the user from accessing the turbine from his property.

Against the withdrawal of the meter (Vulnerability 4).

Against the inclination of the meter (Vulnerability 6): It is reiterated that not all meters are affected by the inclination.

Against the vulnerability of the glass (Vulnerability 1): The only devices that have been found to protect the glass from scratching, perforating or hiting are the “Seguridad Total” and “Casco” devices (Figure 5, I and J). The first was developed by the Peruvian utility EPS GRAU (^{Ziemendorff et al., 2015}). The protection consists of a safety glass, reinforced with an acrylic glass. The other device was developed for the utility Sedapal (Servicio de Agua Potable y Alcantarillado de Lima) (Peru) and is called “Casco”. Its mode of protection of the glass, consists of a thick metal helmet that prevents access to the window, but also to reading. Therefore it has to be opened for reading with a special key.

Against the possibility of perforating the register from the side (Vulnerability 2): The same two devices are the only ones that prevent this type of tampering, protecting the sides of the meter with a metal cast. The “Copa” and “Pulpo” devices could fulfill the same function, however they leave that part of the register without protection, where are the hinges of the meter cover fit (Figure 5, F and H; the arrows indicate the vulnerable part).

Against the possibility of perforating the cast (Vulnerability 3): It only occurs in plastic cast meters, for which, due to its low use, no devices have been developed. The only form of protection is the coating of the meter with a cementitious mass, which presents practical problems (see below).

Against the withdrawal of the meter (Vulnerability 4): Being this form of tampering frequent, all the devices analyzed, with the exception of the anti-wire device, fulfill this function.

Against the withdrawal of the register (Vulnerability 5): The “Gauss” and “Argolla” devices do not fulfill this function, nor the seals mounted on the locknut, nor the anti-wire device (Figure 5, A, B, E, G), while the other do (Figure 5, F, H, I, J). In case of the grids (D) are so narrow that they not allowing the hands to be put in the meter box they also comply with it.

Against the inclination of the meter (Vulnerability 6): The “Gauss” device, the seals on the locknut, the grids and the anti-wire device do not fulfill this function (Figure 5, A, B, D, E), while others do comply (Figure 5, F, G, H, I, J).

Against the accessibility of the turbine through the tube (Vulnerability 7): There is a device, which is mounted at the water outlet of the meter, called an anti-wire device (Figure 5, E). This lets the water pass, but not intrusive object to the meter. Theoretically, it is also feasible to mount a non-return valve, however its cost is much higher (USD 0.2 vs. USD 9 approx.).

Against the use of magnets (Vulnerability 8): The only devices that provide effective security to the meter against the use of magnets, even if it does not have a built-in antimagnetic shield, are the “Casco” and “Seguridad Total” devices . This is because they increase the distance by which the magnet can be attached to the meter, and because they contain iron, which has an effect similar to the shields. Tests were performed using the same meters and magnets mentioned, putting both devices on top. The tests were carried out in Tarapoto, Peru (^{Ziemendorff, 2017}) with the result that both devices only allow a small under-registration in meters without antimagnetic protection at the minimum flow rate and with the largest magnet (Table 5).